Porous inorganic materials of silcon and oxygen

ABSTRACT

The present invention relates to a process for the production of porous inorganic materials or a matrix material containing nanoparticles with high uniformity of thickness and/or high effective surface area and to the materials obtainable by this process. By the above-mentioned process materials with a defined thickness in the region of ±10%, preferably ±5% of the average thickness are available.

This is a divisional of U.S. application Ser. No. 10/542,035, filed asApplication No. PCT/EP03/50229 on Jun. 16, 2003

The present invention relates to a process for the production of porousinorganic materials or a matrix material containing nanoparticles withhigh uniformity of thickness and/or high effective surface area and tothe materials obtainable by this process. By the above-mentioned processmaterials with a defined thickness in the region of ±10%, preferably±5%, of the average thickness are available.

Monodisperse SiO₂ particles of spherical form are, for example, knownfrom U.S. Pat. No. 3,634,588. They are obtained by hydrolyticpolycondensation of alcoholate compounds.

U.S. Pat. No. 3,681,017 discloses a process for preparing microporous,platelet silica particles having a length to thickness ratio of at least5.1 and a surface area of 400 to 500 m²/g, which comprises

(a) forming an ammonium stabilized silicic acid solution,(b) freezing said solution,(c) thawing the effluent solution which contains platelet silicaparticles, and recovering said platelet silica particles.

EP-A-325484 relates to nacreous pigments based on metal-oxide-coatedmica particles or other platy silicate particles which contain a dye ora color pigment. The nacreous pigments are obtained by (a) preparing apreliminary-stage product from platy silicate particles and ametal-oxide coating, b) leaching the thus obtained metal-oxide-coatedparticles with a mineral acid, possibly together with an oxidant, and c)dyeing of the thus produced metal-oxide-coated, porous particles,containing few or no cations, using at least one dye or one colorpigment.

Highly mono-disperse, non-porous, spherical SiO₂ particles having asmall particle size distribution are disclosed in EP-A-275668. Theseparticles are produced by hydrolytic polycondensation of a sol or asuspension of primary particles of tetraelkoxy silanes in alkalinemedium, which are brought to the desired final size by controlledaddition of further tetraalkoxy silane.

The subsequent coating of the spherical SiO₂ particles is described inJP-A-06-011 872.

WO01/57287 discloses a process for producing an interference pigment,wherein a metal oxide layer, especially a titanium oxide layer, a corelayer, especially a silicon oxide layer and a metal oxide layer,especially a titanium oxide layer, are subsequently evaporated on acarrier, and then separated from the carrier.

DE-A-4341162 discloses a process for producing coloured layerscomprising the simultaneous vapor-deposition of a non-absorbing materialand an organic dye from different vaporizers on a substrate, such asglass, metal, ceramics, plastics etc.

EP-A-803 550 describes spherical SiO₂ particles with a size of from 5 to500 nm coated at individual points with TiO₂, Fe₂O₃ or ZrO₂ particleswith a size of less than 60 nm. The coated SiO₂ is prepared by adding asolution of TiCl₄ to an aqueous dispersion of the SiO₂ particles. Theproducts obtained are used for pigmenting paints, printing inks,plastics and coatings or as sunscreen agents.

U.S. Pat. No. 6,103,209 describes a process for preparing porousspherical silica particles substantially consisting in emulsifying anacidic silica sol in a dispersing media, gelifying the microdrops of thesol in the emulsified state and submitting the resulting gel to thermaltreatment in the presence of the emulsifier liquid and of sol gelationbase.

U.S. Pat. No. 6,335,396 describes silica in the form of powder andsubstantially spherical beads or granules which are characterized by aCTAB specific surface of 140 and 240 m²/g and a porous distribution, theporous volume formed by the pores with a diameter of 175 to 275 Å beingless than 50% of the porous volume formed by the pores with diameters of400 Å or less. The silica may be used as reinforcing fillers forelastomers.

It is the object of the present invention to provide a process for theproduction of porous inorganic materials or a matrix material containingnanoparticles, especially porous silicon oxides, with high uniformity ofthickness and/or high effective surface area, by which process materialswith a high degree of plane parallelism and a defined thickness in theregion of ±10%, preferably ±5%, of the average thickness and/or definedporosity can be produced.

Said object has been solved by a process for the production of porousmaterials, comprising the steps of:

a) vapor-deposition of a separating agent onto a carrier to produce aseparating agent layer,b) the simultaneous vapor-deposition of a material and a separatingagent onto the separating agent layer (a),c) the separation of the material from the separating agent.

The term “SiO_(y) with 0.70≦y≦1.80” means that the molar ratio of oxygento silicon at the average value of the silicon oxide layer is from 0.70to 1.80. The composition of the silicon oxide layer can be determined byESCA (electron spectroscopy for chemical analysis).

The term “SiO_(z) with 0.70≦z≦2.0” means that the molar ratio of oxygento silicon at the average value of the silicon oxide layer is from 0.70to 2.0. The composition of the silicon oxide layer can be determined byESCA (electron spectroscopy for chemical analysis).

According to the present invention the term “aluminum” comprisesaluminum and alloys of aluminum. Alloys of aluminum are, for exampledescribed in G. Wassermann in Ullmanns Enzyklopädie der IndustriellenChemie, 4. Auflage, Verlag Chemie, Weinheim, Band 7, p. 281 to 292.Especially suitable are the corrosion stable aluminum alloys describedon page 10 to 12 of WO00/12634, which comprise besides of aluminumsilicon, magnesium, manganese, copper, zinc, nickel, vanadium, lead,antimony, tin, cadmium, bismuth, titanium, chromium and/or iron inamounts of less than 20% by weight, preferably less than 10% by weight.

The term “silicon/silicon oxide layer or flakes” comprisesplane-parallel structures obtainable by heating plane-parallelstructures of SiO_(y) in an oxygen-free atmosphere at a temperatureabove 400° C. and optionally an oxidative heat treatment.

The present invention is directed to porous plate-like (plane-parallel)structures (flakes), in particular SiO_(z) flakes whose particles have alength of from 1 μm to 5 mm, a width of from 1 μm to 2 mm, and athickness of from 20 nm to 1.5 μm, and a ratio of length to thickness ofat least 2:1, the particles having two substantially parallel faces, thedistance between which is the shortest axis of the particles. The porousSiO_(z) flakes are mesoporous materials, i.e. have pore widths of ca. 2to ca. 50 nm. The pores are randomly inter-connected in athree-dimensional way. So, when used as a catalyst or a support, thepassage blockage, which frequently occurs in SiO₂ flakes having atwo-dimensional arrangement of pores can be prevented. Preferably, theporous SiO_(z) flakes have a specific surface of greater than 500 m²/g,especially greater than 600 m²/g. The BET specific surface area isdetermined according to DIN 66131 or DIN 66132 (R. Haul und G. Dümbgen,Chem.-Ing.-Techn. 32 (1960) 349 and 35 (1063) 586) using theBrunauer-Emmet-Teller method (J. Am. Chem. Soc. 60 (1938) 309).

The flakes of the present invention are not of a uniform shape.Nevertheless, for purposes of brevity, the flakes will be referred to ashaving a “diameter.” The silicon/silicon oxide flakes have aplane-parallelism and a defined thickness in the range of ±10%,especially ±5% of the average thickness. The silicon/silicon oxideflakes have a thickness of from 20 to 2000 nm, especially from 100 to500 nm. It is presently preferred that the diameter of the flakes be ina preferred range of about 1-60 μm with a more preferred range of about5-40 μm and a most preferred range of about 5-20 μm. Thus, the aspectratio of the flakes of the present invention is in a preferred range ofabout 2.5 to 625 with a more preferred range of about 50 to 250.

According to the present invention the separating agent used for theseparating agent layer can be different from the separating agent usedfor the layer comprising the material and the separating agent (mixedlayer). Preferably the separating agent used in the separating agentlayer and the mixed layer is identical. Removal of the separating agentis done preferably by dissolving the separating agent in a solvent andseparation of the material from the solvent. Alternatively, an organicseparating agent can be used, in particular, in the mixed layer, whichcan be distilled off under high vacuum at temperatures up to 250° C.Besides the suitable organic separating agents mentioned below, organicpigments, like phthalocyanines, diketopyrrolopyrroles, quinacridonesetc. are suitable.

The platelike material can be produced in a variety of distinctable andreproducible variants by changing only two process parameters: thethickness of the mixed layer of material and separating agent and theamount of the material contained in the mixed layer.

In addition, the present invention is also directed to the porousplatelike materials, in particular SiO_(z) flakes, obtainable by theabove process, wherein 0.70≦z≦2.0, especially 1.4≦z≦2.0, very especiallyz=2.0 as well as porous SiO_(z) flakes, wherein 0.70≦z≦2.0, especially0.95≦z≦2.0, very especially z=2.0.

FIG. 1 is a microphotograph of the porous SiO₂ flakes obtained inexample 1. Pores or better (nano) cavities are discernible. As evidentfrom FIG. 2 these pores or cavities are not limited to the surface ofthe porous SiO₂ flakes.

FIG. 2 is an ultrathin section of a porous SiO₂ flake loaded withpalladium. The metal (black spots) is inside the flakes. The metal spotsize is between 1 and 3 nm.

FIG. 3 shows an atomic force microscope (AFM) picture of the porous SiO₂flakes of example 1. The pore sizes are up to 30 nm.

According to the present invention the porous platelike material isproduced by depositing a mixed layer of material/separating agent on aseparating agent layer. By controlling the amount of separating agent inthe mixed layer the porosity of the material can be controlled in asimple manner.

The mixed layer and the separating agent layer are vapor-deposited invacuo, wherein the separating agent is mixed with the material bysimultaneous vapor-deposition in vacuo. In general, the mixed layercontains the separating agent in an amount of 1 to 60% by weight basedon the total weight of material and separating agent.

The (porous) material is preferably a metal or a metal oxide or anon-metal oxide or a mixture thereof. Most preferred the non-metal oxideis SiO_(z) with 0.70≦z≦2.0, especially 1.4≦z≦2.0. The most preferredmetal oxide is TiO₂.

In general, according to high-resolution electron microscopy the porousmaterials of the present invention have a pore diameter of less than 30nm.

The production of the porous materials is done by vapor depositiontechnique. The substances to be vaporized are heated under a high vacuumand are vaporized. The vapors condense on the cold substrate surfaces,giving the desired thin layers. Vaporization takes place either in metalcontainers (boats of tungsten, molybdenum or tantalum metal sheet),which are heated directly by passage of a current, or by bombardmentwith electron beams.

In the case of the sputtering technique or in the case of cathodeatomization, a gas discharge (plasma) is ignited between the substrateand coating material (target), which is in the form of plates. Thecoating material is bombarded with high-energy ions from the plasma, forexample argon ions, and is thereby abraded or atomized. The atoms andmolecules of the atomized coating material are deposited on thesubstrate and form the desired thin layer.

Metals or alloys are particularly suitable for sputtering techniques.They can be atomized at comparatively high rates, especially in theso-called DC magnetron process. Compounds such as oxides or suboxides ormixtures of oxides can likewise be atomized using high-frequencysputtering. The chemical composition of the layers is determined by thecomposition of the coating material (target). However, it can also beinfluenced by adding substances to the gas which forms the plasma. Oxideor nitride layers, in particular, are produced by addition of oxygen ornitrogen to the gas phase (see, for example, U.S. Pat. No. 5,440,446 undEP-A-733919).

The production is very simple, if the mixed layer is formed by twovaporizers, whose vapor beams overlap, so that the mixed layer iscreated in the overlapping area. Alternatively, the vapor deposition canbe achieved using one vaporizer, which vaporizes both componentssimultaneously or alternately.

Preferably resistance heated evaporators, evaporators heated withelectron beams, evaporators heated inductively or evaporators operatedwith an arc are used as evaporators.

For simplification of separation the carrier material should show asmooth or a structured surface. The movable carrier may consist of oneor more discs, cylinders or other rotationally symmetrical bodies, whichrotate about an axis (cf. WO01/25500), and consists preferably of one ormore continuous metal belts with or without a polymeric coating or ofone or more polyimide or polyethylene terephthalate belts, so that acontinuous material manufacturing is allowed (DE19844357). A polyimidefilm or a film of metal or film of a combination of these materials areespecially suitable as the carrier material.

The separating agent vapor-deposited onto the carrier in step a) may bea lacquer (surface coating), a polymer, such as, for example, the(thermoplastic) polymers, in particular acryl- or styrene polymers ormixtures thereof, as described in U.S. Pat. No. 6,398,999, an organicsubstance soluble in organic solvents or water and vaporizable in vacuo,such as anthracene, anthraquinone, acetamidophenol, acetylsalicylicacid, camphoric anhydride, benzimidazole, benzene-1,2,4-tricarboxylicacid, biphenyl-2,2-dicarboxylic acid, bis(4-hydroxyphenyl)sulfone,dihydroxyanthraquinone, hydantoin, 3-hydroxybenzoic acid,8-hydroxyquinoline-5-sulfonic acid monohydrate, 4-hydroxycoumarin,7-hydroxycoumarin, 3-hydroxynaphthalene-2-carboxylic acid, isophthalicacid, 4,4-methylene-bis-3-hydroxynaphthalene-2-carboxylic acid,naphthalene-1,8-dicarboxylic anhydride, phthalimide and its potassiumsalt, phenolphthalein, phenothiazine, saccharin and its salts,tetraphenylmethane, triphenylene, triphenylmethanol or a mixture of atleast two of those substances. The separating agent is preferably aninorganic salt soluble in water and vaporizable in vacuo (see, forexample, DE 198 44 357), such as sodium chloride, potassium chloride,lithium chloride, sodium fluoride, potassium fluoride, lithium fluoride,calcium fluoride, sodium aluminum fluoride and disodium tetraborate.

Preferred embodiments of the present invention are described in moredetail below:

The vapor-deposition in steps a) and b) is carried out preferably undera vacuum of <0.5 Pa. The dissolution of the separating agent layer instep c) is carried out at a pressure in the range preferably from 1 to5×10⁴ Pa, especially from 600 to 10⁴ Pa, and more especially from 10³ to5×10³ Pa.

In a preferred embodiment of the present invention the following layersare subsequently vapor-deposited under a vacuum of preferably 10⁻¹ to10⁻³ Pa, more preferably 1 to 10⁻³ Pa, by thermal evaporation accordingto the PVD technique:

-   -   a separating agent layer and    -   a mixed layer of the material and the separating agent in the        desired amount on top of the separating agent layer, which is        incorporated into the material by simultaneous vapor-deposition        using two vaporizers or alternatively one vaporizer.

In principle, every inorganic material can be used in the processaccording to the present invention, which is processable under theconditions of the inventive process. Metals, metal oxides and/ornon-metal oxides are preferably used.

If the material is a metal oxide, it is preferably selected from thegroup selected from titanium suboxides, zirconium monoxide, niobiumoxide, cerium-metal (treatment in air results in CeO₂), such ascommercial available cerium mixed metal.

If the material is a metal, metals, such as aluminum, nickel, iron,cobalt, silver, chromium, zirconium, niobium, molybdenum, vanadium,titanium or alloys, such as chromium-nickel, iron-nickel, iron-chromium,nickel-cobalt etc. are preferred. The evaporation of alloys ispractically carried out using different vaporizers and by maintainingthe desired mol ratio.

A particular preferred embodiment of the present invention is directedto the production of porous SiO_(z) flakes: A salt, for example NaCl,followed successively by a layer of silicon suboxide (SiO_(y)) andseparating agent, especially NaCl or an organic separating agent, isvapor-deposited onto a carrier, which may be a continuous metal belt,passing by way of the vaporizers under a vacuum of <0.5 Pa.

The mixed layer of silicon suboxide (SiO_(y)) and separating agent isvapor-deposited by two distinct vaporizers, which are each charged withone of the two materials and whose vapor beams overlap, wherein theseparating agent is contained in the mixed layer in an amount of 1 to60% by weight based on the total weight of the mixed layer.

The thicknesses of salt vapor-deposited are about 20 nm to 100 nm,especially 30 to 60 nm, those of the mixed layer from 20 to 2000 nm,especially 50 to 500 nm depending upon the intended purpose of theproduct.

On its further course, the belt-form carrier, which is closed to form aloop, runs through dynamic vacuum lock chambers of known mode ofconstruction (cf. U.S. Pat. No. 6,270,840) into a region of from 1 to5×10⁴ Pa pressure, preferably from 600 to 10⁴ Pa pressure, andespecially from 10³ to 5×10³ Pa pressure, where it is immersed in adissolution bath. The temperature of the solvent should be so selectedthat its vapor pressure is in the indicated pressure range. Withmechanical assistance, the separating agent layer and if the separatingagent of the mixed layer is similar to the separating agent of theseparating agent layer, the separating agent contained in the SiO_(z)layer rapidly dissolves and the product layer breaks up into flakes,which are then present in the solvent in the form of a suspension. Iftwo different separating agents are used, the step of dissolving theseparating agent of the separating agent layer is followed by the stepof dissolving the separating agent of the mixed layer. In a preferredembodiment the separating agent of the separating agent layer is NaCland the separating agent of the mixed layer is an organic separatingagent, such as phenolphthalein, wherein the NaCl is dissolved in wateror aqueous solutions (for example hydrochloric acid) and the organicseparating agent is dissolved in an organic solvent, like iso-propanol,or sublimed. On its further course, the belt is dried and freed from anycontaminants still adhering to it. It runs through a second group ofdynamic vacuum lock chambers back into the vaporization chamber, wherethe process of coating with separating agent and product layer ofSiO_(y)/separating agent is repeated.

The suspension then present in both cases, comprising product structuresand solvent, and the separating agent dissolved therein, is thenseparated in a further operation in accordance with a known technique.For that purpose, the product structures are first concentrated in theliquid and rinsed several times with fresh solvent in order to wash outthe dissolved separating agent. The product, in the form of a solid thatis still wet, is then separated off by filtration, sedimentation,centrifugation, decanting or evaporation.

A SiO_(1.00-1.8) layer is formed preferably from silicon monoxide vapourproduced in the vaporiser by reaction of a mixture of Si and SiO₂ attemperatures of more than 1300° C.

A SiO_(0.70-0.99) layer is formed preferably by evaporating siliconmonoxide containing silicon in an amount up to 20% by weight attemperatures of more than 1300° C.

The production of porous SiO_(z) flakes with z>1 can be achieved byproviding additional oxygen during the evaporation. For this purpose thevacuum chamber can be provided with a gas inlet, by which the oxygenpartial pressure in the vacuum chamber can be controlled to a constantvalue.

Alternatively, after drying, the product can be subjected to oxidativeheat treatment. Known methods are available for that purpose. Air orsome other oxygen-containing gas is passed through the plane-parallelstructures of SiO_(y) wherein y is, depending on the vapor-depositionconditions, from 0.70, especially 1 to about 1.8, which are in the formof loose material or in a fluidized bed, at a temperature of more than200° C., preferably more than 400° C. and especially from 500 to 1000°C. After several hours all the structures will have been oxidised toSiO₂. The product can then be brought to the desired particle size bymeans of grinding or air-sieving and delivered for further use.

The porous SiO_(z) flakes should have a minimum thickness of 50 nm, tobe processable. The maximum thickness is dependent on the desiredapplication. For applications, in which interference plays an importantrole, the thickness is in the range of from 150 to 500 nm.

In order to achieve orientation of the porous plane-parallel structuresof silicon dioxide approximately parallel to the surface of the surfacecoating layer(s), the surface tension of the structures can be modifiedby adding known chemicals to the surface coating, for example by meansof commercially available silane oligomers. Such oligomers, known underthe trade names DYNASILAN™, HYDROSIL™, PROTECTOSIL™ can also bedeposited directly onto the surface of the plane-parallel structures,either from a liquid phase or by condensation, before the latter areintroduced into the surface coating. Because such organic oligomers haveonly limited temperature resistance, it has proved advantageous to carryout such treatment only after oxidation to SiO₂ has taken place, attemperatures from 0° to 250° C.

The porous plane-parallel structures of silicon dioxide can beincorporated into a surface coating or dispersion layer for increasingthe resistance to abrasion (scratch resistance) and resistance to impactof the surface of such a surface coating or dispersion.

In addition, the surface of the porous plane-parallel structures ofsilicon dioxide can be rendered hydrophobic by derivatization withtypical silane coupling agents having the formula ClSiX¹X²X³, whereinX¹, X² and X³ represent organic groups and can be the same or different.Alternatively, the silica surface can be alkylated by first chlorinatingthe silica surface using thionyl chloride and then metathesizing withalkyllithium to introduce alkyl groups and eliminate LiCl (J. D. Sunseriet al., Langmuir 19 (2003) 8608-8610).

In a further embodiment the present invention relates to porousplatelike SiO_(y+a) particles, containing (1−y/y+a) silicon, wherein0.70≦y≦1.8, especially 1.0≦y≦1.8, 0.05≦a≦1.30, and the sum of y and a issmaller or equal to 2.

Porous SiO_(y+a) flakes, especially SiO₂ flakes containing (1−y/y+a) Sinanoparticles can be obtained by heating porous SiO_(y) particles in anoxygen-free atmosphere, i.e. an argon or helium atmosphere or in avacuum of less than 13 Pa (10⁻¹ Torr), at a temperature above 400° C.,especially 400 to 1100° C.

It is assumed that by heating SiO_(y) particles in an oxygen-freeatmosphere, SiO_(y) disproportionates in SiO₂ and Si:

SiO_(y)→(y/y+a)SiO_(y+a)+(1−y/y+a)Si

In this disproportion porous SiO_(y+a) flakes are formed, containing(1−(y/y+a)) Si, wherein 0.70≦y≦1.8, especially 0.70≦y≦0.99 or 1≦y≦1.8,0.05≦a≦1.30, and the sum y and a is equal or less than 2. SiO_(y+a) isan oxygen enriched silicon suboxide. The complete conversion of SiO_(y)in Si and SiO₂ is preferred:

SiO_(y)→(y/2)SiO₂+(1−(y/2))Si

In the temperature range of from 400 to 900° C. the formed silicon isamorph. In the temperature range of from 900 to 1100° C. siliconcrystallites are formed. The average crystallite size is in the range offrom 1 to 20 nm, especially 2 to 10 nm. The size is on the one handdependent on the temperature. That is, at 1100° C. larger crystallitesthan at 900° C. are formed. On the other hand a clear tendency for theformation of smaller crystallites is found, the higher the oxygen levelof the SiO_(y) is. Depending on the preparation the Si containing,plane-parallel SiO_(y+a) particles, especially SiO₂ particles can showphotoluminescence.

The porous silicon/silicon oxide flakes should have a minimum thicknessof 50 nm, to be processable. The maximum thickness is dependent on thedesired application. For applications, in which interference plays animportant role, the thickness is in the range of from 150 to 500 nm.

The further layers necessary for interferences can be deposited inaccordance with usual procedures known for effect pigments with micaand/or SiO₂ core, which will be described in more detail below by meansof the porous SiO_(z) flakes.

It is furthermore possible to convert plane-parallel structures of theporous SiO_(y), starting from their surface, partially to siliconcarbide (SiC) (in the context of the present Application, this procedureshall be referred to as “carburization”). For that purpose, theplane-parallel porous SiO_(y) structures are caused to react in agas-tight reactor heatable to a maximum of about 1500° C., preferably inthe form of loose material, with a carbon-containing gas selected fromalkynes, for example acetylene, alkanes, for example methane, alkenes,aromatic compounds or the like, and mixtures thereof optionally inadmixture with an oxygen containing compound, such as, for example,aldehydes, ketones, water, carbon monoxide, carbon dioxide or the like,or mixtures thereof, at from 500 to 1500° C., preferably from 500 to1000° C., and advantageously with the exclusion of oxygen. In order totemper the reaction, an inert gas, for example argon or helium, may beadmixed with the carbon-containing gas. In such carburization, it ispossible for all of the SiO_(y) to be reacted to form SiC; preferablyfrom 5 to 90% by weight of the SiO_(y) are reacted to form SiC.

Consequently, the present invention relates also to plane-parallelstructures (pigments) based on porous plane-parallel silicon oxidesubstrates having on their surface a layer comprising silicon carbide(SiC). The SiO_(y)-to-SiC reaction takes place starting from the surfaceof the plane-parallel structures and accordingly results in a gradientrather than a sharp transition. This means that, in that embodiment, theSiC-containing layer consists of (silicon/silicon oxide)_(a) and(SiC)_(b), wherein 0≦a<1 and 0<b≦1, with b being 1 and a being 0 closeto the surface of the pigment and the amount of SiC approaching 0 closeto the boundary with the silicon/silicon oxide substrate.

The remaining SiO_(y) of the plane-parallel structures may be oxidizedin a further step at a temperature of at least about 200° C. up to about400° C. with an oxygen-containing gas, such as air.

After carbide formation has been terminated, it is possible, optionally,for residual SiO_(y) still present in the plane-parallel structures tobe converted into SiO₂ by oxidation with an oxygen-containing gas, suchas air, at a temperature of at least 200° C. without destroying the SiCformed. Because of the large specific surface area of the plane-parallelstructures, temperatures of about 400° C. should not, in this case, beexceeded in the presence of oxygen.

The porous (carburised) silicon oxide flakes having a preferredthickness in the range of from 50 to 2000 nm are novel and form afurther subject of the present invention. They may be used, for example,as corrosion-resistant additives having a Mohs hardness of from 8 to 9in coatings or as corrosion-resistant additives in coating compositionsin order to obtain properties of selective reflection in the infra-red.In addition the porous (carburised) silicon oxide flakes can be used assubstrates for interference pigments. The pigments are highlyshear-stable and, in plastics, surface coatings or printing inks, resultin high degrees of saturation and excellent fastness properties andalso, in the case of interference pigments, a high degree ofgoniochromicity (see, for example PCT/EP03101323).

Owing to high chemical and thermal stabilities, large surface areas andgood compatibilities with other materials, the porous silicon oxideflakes can be used for many purposes, such as, for example, in thefields of selective separation (M. Asaeda, S. Yamasaki, Separation ofinorganic/organic gas mixtures by porous silica membranes, Sep. Purif.Technol. 25 (2001) 151-159), catalysis (H. Suquet, S. Chevalier, C.Marcilly, D. Barthomeuf, Preparation of porous materials by chemicalactivation of the Lanovermiculite, Clay Miner. 26 (1991) 49-60; Y. Deng,C. Lettmann, W. F. Maier, Leaching of amorphous V- and Ti-containingporous silica catalysts in liquid phase oxidation reactions, Appl.Catal. A 214 (2001) 31-45; M. O. Coppens, J. H. Sun, T. Maschmeyer,Synthesis of hierarchical porous silicas with a controlled pore sizedistribution at various length scales, Catal. Today 69 (2001) 331-335),dielectric materials (A. Jain, S. Rogojevic, S. Ponoth, N. Agarwal, I.Matthew, W. N. Gill, P. Persans, M. Tomozawa, J. L. Plawsky, E. Simonyi,Porous silica materials as low-k dielectrics for electronic and opticalinterconnects, Thin Solid Films 398-399 (2001) 513-522, prostheticmaterials (J. M. Gomez-Vega, M. Iyoshi, K. Y. Kim, A. Hozumi, H.Sugimura, O. Takai, Spin casted mesoporous silica coatings for medicalapplications, Thin Solid Films 398-399 (2001) 615-20), or the use ofporous silica as gas adsorbents (K. Okada, A. Shimai, T. Takei, S.Hayashi, A. Yasumori, K. J. D. MacKenzie, Preparation of microporoussilica from metakaolinite by selective leaching method, MicroporousMesoporous Mater. 21 (1998) 289-296), heavy metal ion adsorbents (B.Lee, Y. Kim, H. Lee, J. Yi, Synthesis of functionalized porous silicasvia templating method as heavy metal ion adsorbents: the introduction ofsurface hydrophilicity onto the surface of adsorbents, MicroporousMesoporous Mater. 50 (2001) 77-90, molecular sieves (U.S. Pat. No.5,958,368), as carrier for drug delivery exhibiting a delayed releaseeffect (J. F. Chen, H. M. Ding, J. X. Wang, L. Shao, Biomaterials 25(2004) 723-727), for the production of an electrokinetic microchannelbattery (J. Yang, F. Lu, L. W. Kostiuk, D. Y. Kwok, J. Micromech.Microeng. 13 (2003) 963-970), and inorganic carriers for enzymeimmobilization (F. He, R. X. Zhuo, L. J. Liu, D. B. Jin, J. Feng, X. L.Wang, Immobilized lipase on porous silica beads: preparation andapplication for enzymatic ring-opening polymerization of cyclicphosphate, Reactive Functional Polym. 47 (2001) 153-89), especially ascarrier for catalytic systems, for example, for olefin polymerisation orSuzuki coupling, or as reinforcing fillers for elastomers, especiallytires or silicon rubbers (see, for example, U.S. Pat. No. 6,335,396 andEP-A-407262).

The SiO_(z) flakes appear to be ideal for supporting catalytic metals,such as copper or nickel based reforming catalysts, or palladium basedcatalysts for the Suzuki reaction. These particles have very highsurface areas (˜700 m²/g), and nanoscale (2-50 nm) porosity.

In a particularly preferred embodiment of the present invention, theporous SiO_(z) flakes are used in an ink-receptive layer of imagablemedia. Accordingly, the present invention also relates to an imagablemedia comprising a support and an ink-receptive layer containing porousSiO_(z) flakes and a hydrophilic binder, wherein 0.70≦z≦2.0, especially1.40≦z≦2.0.

In the present invention, a range of the total amount of the poroussilica flakes to be used in the ink-receptive layer is preferably 2 to30 g/m². The above-mentioned range is preferred in the points ofink-absorption property and strength of the ink-receptive layer.

As the support to be used in the present invention, there may be usedplastic resin films such as polyethylene, polypropylene, polyvinylchloride, diacetate resin, triacetate resin, cellophane, acrylic resin,polyethylene terephthalate, polyethylene naphthalate, etc., waterresistance supports such as a resin-coated paper in which a polyolefinresin is laminated on the both surfaces of paper, or water-absorptivesupports such as fine quality paper, art paper, coated paper, castcoated paper and the like. A water resistance support is preferablyused. A thickness of these supports to be used is preferably in therange of about 50 to 250 μm.

To the ink-receptive layer of the present invention, a hydrophilicbinder is added to maintain the characteristics as a film. As thehydrophilic binder to be used, those conventionally known various kindsof binders can be used, and a hydrophilic binder which has hightransparency and gives high permeability of ink is preferably used. Forusing the hydrophilic binder, it is important that the hydrophilicbinder does not clog the voids by swelling at the initial stage ofpermeation of ink. From this point of view, a hydrophilic binder havinga relatively low swellability at around room temperature is preferablyused. A particularly preferred hydrophilic binder is a completely orpartially saponified polyvinyl alcohol or a cationic-modified polyvinylalcohol.

Among the polyvinyl alcohols, particularly preferred is partially orcompletely saponified polyvinyl alcohol having a saponification degreeof 80% or more. Polyvinyl alcohols having an average polymerizationdegree of 500 to 5000 are preferred.

Also, as the cationic-modified polyvinyl alcohol, there may bementioned, for example, a polyvinyl alcohol having a primary to tertiaryamino groups or a quaternary ammonium group at the main chain or sidechain of the polyvinyl alcohol as disclosed in Japanese ProvisionalPatent Publication No. 10483/1986.

Also, other hydrophilic binder may be used in combination, but an amountthereof is preferably 20% by weight or less based on the amount of thepolyvinyl alcohol.

In the ink-receptive layers according to the present invention, a weightratio of the porous SiO₂ particles and the hydrophilic binder ispreferably in the range of 60:40 to 92:8, more preferably 70:30 to90:10.

In the ink-receptive layer of the present invention, other inorganicfine particles than porous silica flakes may be contained in an amountof about 30% by weight or less of the amount of the porous silicaflakes.

In the present invention, it is preferred that the ink-receptive layer Bcontains fine particles having an average particle size of 3 to 10 μm.As the fine particles, inorganic or organic fine particles may be used,and preferably organic resin fine particles. By adding theabove-mentioned fine particles to the ink-receptive layer B, unevenglossiness can be overcome when printing is carried out by using pigmentink.

Embodiments of the present invention are possible in which the inkreceptive layer includes additional materials in particle and/or granuleform. Examples of materials which may be suitable in some applicationsinclude calcium carbonate, fumed silica, precipitated silica alumina,alkyl quaternary ammonium bentonite, alkyl quaternary ammoniummontmorillonite, clay, kaolin, talcum, titanium oxide, chalk, bentonite,aluminum silicate calcium silicate, magnesium carbonate, calciumsulfate, barium sulfate, silicium oxide barium carbonate, boehmite,pseudo boehmite, aluminum oxide, aluminum hydroxide diatomaceous earth,calcined clay, and the like. Additional particles may serve variousfunctions including ink retention. Examples of particle functionsinclude pigmentation filling, lubricating, ultraviolet light absorption,whitening, heat stabilizing, and the like.

As the above-mentioned organic resin fine particles, there may bementioned, for example, olefin homopolymer or copolymer such aspolyethylene, polypropylene, polyisobutyrene, polyethylene oxide,polytetrafluoroethylene, polystyrene, ethylene-(meth)acrylic acidcopolymer, ethylene-(meth)acrylate copolymer, ethylene-vinyl acetatecopolymer and the like or a derivative thereof, polyvinyl chloride,vinyl chloride-vinyl acetate copolymer, vinyl chloride-(meth)acrylatecopolymer, polyvinylidene chloride, styrene-butadiene rubber, NBR rubberand the like, singly or in admixture thereof. Incidentally,(meth)acrylic acid or (meth)acrylate herein means acrylic acid and/ormethacrylic acid, or acrylate and/or methacrylate.

The respective layers of the ink-receptive layers according to thepresent invention may preferably contain a cationic compound for thepurpose of improving water resistance. As the cationic compounds, theremay be mentioned a cationic polymer and a water-soluble metalliccompound. As the cationic polymer, there may be preferably mentionedpolyethyleneimine, polydiallylamine, polyallylamine, polyalkylamine, aswell as polymers having a primary to tertiary amino group or aquaternary ammonium salt group. The molecular weight (a weight averagemolecular weight; Mw) of these cationic polymers is preferably about5,000 to about 100,000.

As the water-soluble metallic compound to be used in the presentinvention, there may be mentioned, for example, a water-solublepolyvalent metallic salt. There may be mentioned a water-soluble salt ofa metal selected from the group consisting of calcium, barium,manganese, copper, cobalt, nickel, aluminum, iron, zinc, zirconium,titanium, chromium, magnesium, tungsten, and molybdenum. Morespecifically, there may be mentioned, for example, calcium acetate,calcium chloride, calcium formate, calcium sulfate, barium acetate,barium sulfate, barium phosphate, manganese chloride, manganese acetate,manganese formate dehydrate, ammonium manganese sulfate hexahydrate,cupric chloride, copper (II) ammonium chloride dihydrate, coppersulfate, cobalt chloride, cobalt thiocyanate, cobalt sulfate, nickelsulfate hexahydrate, nickel chloride hexahydrate, nickel acetatetetrahydrate, ammonium nickel sulfate hexahydrate, amide nickel sulfatetetrahydrate, aluminum sulfate, aluminum sulfite, aluminum thiosulfate,poly(aluminum chloride), aluminum nitrate nonahydrate, aluminum chloridehexahydrate, ferrous bromide, ferrous chloride, ferric chloride, ferroussulfate, ferric sulfate, zinc bromide, zinc chloride, zinc nitratehexahydrate, zinc sulfate, titanium chloride, titanium sulfate,zirconium acetate, zirconium chloride, zirconium oxychlorideoctahydrate, zirconium hydroxychloride, zirconium nitrate, basiczirconium carbonate, zirconium hydroxide, zirconium lactate, ammoniumzirconium carbonate, potassium zirconium carbonate, zirconium sulfate,zirconium fluoride, chromium acetate, chromium sulfate, magnesiumsulfate, magnesium chloride hexahydrate, magnesium citrate nonahydrate,sodium phosphorus wolframate, tungsten sodium citrate,dodecawolframatophosphate n hydrate, dodecawolframatosilicate 26hydrate, molybdenum chloride, dodecamolybdatephosphate n hydrate, etc.Of these, the zirconium type compounds having high transparency andwater resistance improvement effects are preferably used.

The ink-receptive layers of the present invention may contain variouskinds of oil droplets to improve brittleness of a film. As such oildroplets, there may be contained a hydrophobic high-boiling pointorganic solvent (for example, liquid paraffin, dioctyl phthalate,tricresyl phosphate, silicone oil, etc.) or polymer particles (forexample, particles in which at least one of a polymerizable monomer suchas styrene, butyl acrylate, divinyl benzene, butyl methacrylate,hydroxyethyl methacrylate, etc. is/are polymerized) each having asolubility in water at room temperature of 0.01% by weight or less. Suchoil droplets can be used in an amount in the range of 10 to 50% byweight based on the amount of the hydrophilic binder,

In the present invention, a cross-linking agent (hardening agent) of thehydrophilic binder may be used in the ink-receptive layers. Specificexamples of the hardening agent may include an aldehyde type compoundsuch formaldehyde and glutaraldehyde, a ketone compound such as diacetyland chloropentanedione,bis(2-chloroethylurea)-2-hydroxy-4,6-dichloro-1,3,5-triazine, a compoundhaving a reactive halogen as disclosed in U.S. Pat. No. 3,288,775,divinylsulfone, a compound having a reactive olefin as disclosed in U.S.Pat. No. 3,635,718, a N-methylol compound as disclosed in U.S. Pat. No.2,732,316, an isocyanate compound as disclosed in U.S. Pat. No.3,103,437, an aziridine compound as disclosed in U.S. Pat. Nos.3,017,280 and 2,983,611, a carbodiimide type compound as disclosed inU.S. Pat. No. 3,100,704, an epoxy compound as disclosed in U.S. Pat. No.3,091,537, a halogen carboxyaldehyde compound such as mucochloric acid,a dioxane derivative such as dihydroxydioxane, an inorganic hardeningagent such as chromium alum, zirconium sulfate, boric acid and a borate,and they may be used singly or in combination of two or more.

Among the hardening agents as mentioned above, boric acid and a borateare particularly preferred. As the boric acid to be used in the presentinvention, orthoboric acid, metaboric acid, hypoboric acid, and the likemay be mentioned, and as the borate, a sodium salt, a potassium salt, anammonium salt thereof may be mentioned. A content of the boric acid orborate is preferably 0.5 to 80% by weight in the ink-receptive layerbased on the amount of the polyvinyl alcohol.

In the present invention, to the respective layers of the ink-receptivelayers, various kinds of conventionally known additives such as acoloring dye, a coloring pigment, a fixing agent of an ink dye, an UVabsorber, an antioxidant, a dispersant of the pigment, an antifoamingagent, a leveling agent, an antiseptic agent, a fluorescent brightener,a viscosity stabilizer, a pH buffer, etc. may be added in addition tothe hardening agent.

An imagable media in accordance with the present invention may beutilized to fabricate identification cards, driver's licenses,passports, and the like. In a preferred embodiment, the image receptivematerial is adapted to receive an image comprised of aqueous ink. In aparticularly preferred embodiment, the image receptive material isadapted to receive an image comprised of aqueous pigmented ink adaptedfor use in an inkjet printer. A printed image in accordance with thepresent invention preferably includes one or more security indicia.Examples of security indicia that may be suitable in some applicationsinclude a picture of a human face, a representation of a human fingerprint, barcodes, and/or a representation of a cardholders signature.

Porous SiO_(z) flakes, loaded with organic or inorganic pigments, resultin transparent, easy dispersible particles. Inorganic pigments include;especially those selected from the group consisting of metal oxides,antimony yellow, lead chromate, lead chromate sulfate, lead molybdate,ultramarine blue, cobalt blue, manganese blue, chrome oxide green,hydrated chrome oxide green, cobalt green and metal sulfides, such ascerium or cadmium sulfide, cadmium sulfoselenides, zinc ferrite, bismuthvanadate and mixed metal oxides. Examples of organic pigments (and alsosubstituted derivatives thereof that may be used are described, forexample, in W. Herbst, K. Hunger, Industrielle Organische Pigmente, 2ndcompletely revised edition, VCH 1995: 1-aminoanthraquinone pigments: p.503-511; anthraquinone pigments: p. 504-506, 513-521 and 521-530;anthrapyrimidine: p. 513-415; azo pigments: p. 219-324 and 380-398;azomethine pigments: p. 402-411; quinacridone pigments: p. 462-481;quinacridone quinone pigments: p. 467-468; quinophthalone pigments: p.567-570; diketopyrrolopyrrole pigments: p. 570-574; dioxazine pigments:p. 531-538; flavanthrone pigments: p. 517-519, 521; indanthronepigments: p. 515-517; isoindoline pigments: p. 413-429; isoindolinonepigments: p. 413-429; isoviolanthrene pigments: p. 528-530; perinonepigments: p. 482-492; perylene pigments: p. 482-496; phthalocyaninepigments: p. 431-460; pyranthrone pigments: p. 522-526; thioindigopigments (indigo pigments): p. 497-500, it also being possible to usemixtures of such pigments, including solid solutions. The term pigmentincludes also luminescent materials. Such SiO_(z) flakes can beobtained, for example, by mixing the SiO_(z) flakes with the organicpigment in a medium in which the pigment is soluble, such as, forexample, concentrated H₂SO₄, precipitating the pigment by addition of amedium, such as, for example, water, in which the pigment is insoluble,and isolating the pigmented SiO_(z) flakes by filtration and drying. Theporous SiO_(z) flakes loaded with a pigment can be used for pigmenting asubstrate, like, for example, a high-molecular weight organic material.

Preferably the porous SiO_(z) flakes loaded with a pigment can beobtained by filling the pigment with a so-called latent pigment andconversion of the latent pigment in the pigment form. The pigmentationof porous materials with latent pigments and preferred latent pigmentsare, for example, described in EP-A-648770, EP-A-648817, EP-A-764628,EP-A-761772, EP-A-1086984, WO98/32802, WO00/63297 and PCT/EP03/10968.

The latent pigment generally has the following formula A(B)_(x) (I)wherein

x is an integer from 1 to 8,A is the radical of a chromophore of the quinacridone, anthraquinone,perylene, indigo, quinophthalone, indanthrone, isoindolinone,isoindoline, dioxazine, azo, phthalocyanine or diketopyrrolopyrroleseries, which is linked to x groups B by one or more hetero atoms, thosehetero atoms being selected from the group consisting of nitrogen,oxygen and sulfur and forming part of the radical A,B is a group of the formula

it being possible for the groups B, when x is a number from 2 to 8, tobe the same or different, andL is any desired group suitable for imparting solubility.L is preferably a group of formula

wherein Y¹, Y² and Y³ are independently of each other C₁-C₆alkyl,Y⁴ and Y⁸ are independently of each other C₁-C₆alkyl, C₁-C₆alkylinterrupted by oxygen, sulfur or N(Y¹²)₂, or unsubstituted orC₁-C₆alkyl-, C₁-C₆alkoxy-, halo-, cyano- or nitro-substituted phenyl orbiphenyl,Y⁵, Y⁶ and Y⁷ are independently of each other hydrogen or C₁-C₆alkyl,Y⁹ is hydrogen, C₁-C₆alkyl or a group of formula

Y¹⁰ and Y¹¹ are each independently of the other hydrogen, C₁-C₆alkyl,C₁-C₆alkoxy, halogen, cyano, nitro, N(Y¹²)₂, or unsubstituted or halo-,cyano-, nitro-, C₁-C₆alkyl- or C₁-C₆alkoxy-substituted phenyl,Y¹² and Y¹³ are C₁-C₆alkyl, Y¹⁴ is hydrogen or C₁-C₆alkyl, and Y¹⁵ ishydrogen, C₁-C₆alkyl, or unsubstituted or C₁-C₆alkyl-substituted phenyl,Q is p, q-C₂-C₆alkylene unsubstituted or mono- or poly-substituted byC₁-C₆alkoxy, C₁-C₆alkylthio or C₂-C₁₂dialkylamino, wherein p and q aredifferent position numbers,X is a hetero atom selected from the group consisting of nitrogen,oxygen and sulfur, m being the number 0 when X is oxygen or sulfur and mbeing the number 1 when X is nitrogen, andL¹ and L² are independently of each other unsubstituted or mono- orpoly-C₁-C₁₂alkoxy-, —C₁-C₁₂alkylthio-, —C₂-C₂₄dialkylamino-,—C₆-C₁₂aryloxy-, —C₆-C₁₂arylthio-,—C₇-C₂₄alkylarylamino- or —C₁₂-C₂₄diarylamino-substituted C₁-C₆alkyl or[-(p′,q′-C₂-C₆alkylene)-Z-]_(n)-C₁-C₆alkyl, n being a number from 1 to1000, p′ and q′ being different position numbers, each Z independentlyof any others being a hetero atom oxygen, sulfur orC₁-C₁₂alkyl-substituted nitrogen, and it being possible forC₂-C₆alkylene in the repeating [-C₂-C₆alkylene-Z-] units to be the sameor different,and L₁ and L₂ may be saturated or unsaturated from one to ten times, maybe uninterrupted or interrupted at any location by from 1 to 10 groupsselected from the group consisting of —(C═O)— and —C₆H₄—, and may carryno further substituents or from 1 to 10 further substituents selectedfrom the group consisting of halogen, cyano and nitro. Of specialinterest are compounds of formula (I) wherein L is C₁-C₆alkyl,C₂-C₆alkenyl or

wherein Q is C₂-C₄alkylene, andL¹ and L² are [—C₂-C₁₂alkylene-Z-]_(n)-C₁-C₁₂alkyl or is C₁-C₁₂alkylmono- or poly-substituted by C₁-C₁₂alkoxy, C₁-C₁₂alkylthio orC₂-C₂₄dialkylamino, and m and n are as defined hereinbefore.

Of very special interest are compounds of formula (I) wherein L isC₄-C₅alkyl, C₃-C₆alkenyl or

wherein Q is C₂-C₄alkylene, X is oxygen and m is zero, and L¹ is[—C₂-C₁₂alkylene-O-]_(n)—C₁-C₁₂alkyl or is C₁-C₁₂alkyl mono- orpoly-substituted by C₁-C₁₂alkoxy, especially those wherein -Q-X— is agroup of formula —C(CH₃)₂—CH₂—O—.

Examples of suitable compounds of formula (I) are disclosed in EP-A-0648 770, EP-A-0 648 817, EP-A-0 742 255, EP-A-0 761 772, WO98/32802,WO98/45757, WO98/58027, WO99/01511, WO00/17275, WO00/39221, WO00/63297and EP-A-1 086 984.

The pigment precursors may be used singly or also in mixtures with otherpigment precursors or with colorants, for example customary dyes for theapplication in question.

A is the radical of known chromophores having the basic structureA(H)_(x), wherein A preferably has, at each hetero atom linked to xgroups B, at least one immediately adjacent or conjugated carbonylgroup, such as, for example,

wherein, for example, Z is

and x″ is a number from 1 to 16, especially from 1 to 4;and also, in each case, all known derivatives thereof.

Worthy of special mention are those soluble chromophores wherein thepigment of formula A(H)_(x) is Colour Index Pigment Yellow 13, PigmentYellow 73, Pigment Yellow 74, Pigment Yellow 83, Pigment Yellow 93,Pigment Yellow 94, Pigment Yellow 95, Pigment Yellow 109, Pigment Yellow110, Pigment Yellow 120, Pigment Yellow 128, Pigment Yellow 139, PigmentYellow 151, Pigment Yellow 154, Pigment Yellow 175, Pigment Yellow 180,Pigment Yellow 181, Pigment Yellow 185, Pigment Yellow 194, PigmentOrange 31, Pigment Orange 71, Pigment Orange 73, Pigment Red 122,Pigment Red 144, Pigment Red 166, Pigment Red 184, Pigment Red 185,Pigment Red 202, Pigment Red 214, Pigment Red 220, Pigment Red 221,Pigment Red 222, Pigment Red 242, Pigment Red 248, Pigment Red 254,Pigment Red 255, Pigment Red 262, Pigment Red 264, Pigment Brown 23,Pigment Brown 41, Pigment Brown 42, Pigment Blue 25, Pigment Blue 26,Pigment Blue 60, Pigment Blue 64, Pigment Violet 19, Pigment Violet 29,Pigment Violet 32, Pigment Violet 37,3,6-di(4′-cyano-phenyl)-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione,3,6-di(3,4-dichloro-phenyl)-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dioneor3-phenyl-6-(4′-tert-butyl-phenyl)-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione.Further examples are described by Willy Herbst and Klaus Hunger in“Industrial Organic Pigments” (ISBN 3-527-28161-4, VCH/Weinheim 1993).

Alkyl or alkylene may be straight-chained, branched, monocylic orpolycyclic.

C₁-C₁₂Alkyl is accordingly, for example, methyl, ethyl, n-propyl,isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, cyclobutyl,n-pentyl, 2-pentyl, 3-pentyl, 2,2-dimethylpropyl, cyclopentyl,cyclohexyl, n-hexyl, n-octyl, 1,1,3,3-tetramethylbutyl, 2-ethylhexyl,nonyl, trimethylcyclohexyl, decyl, menthyl, thujyl, bornyl, 1-adamantyl,2-adamantyl or dodecyl.

When C₂-C₁₂alkyl is mono- or poly-unsaturated, it is C₂-C₁₂alkenyl,C₂-C₁₂alkynyl, C₂-C₁₂alkapolyenyl or C₂-C₁₂alkapolyynyl, it beingpossible for two or more double bonds to be, where appropriate, isolatedor conjugated, such as, for example, vinyl, allyl, 2-propen-2-yl,2-buten-1-yl, 3-buten-1-yl, 1,3-butadien-2-yl, 2-cyclobuten-1-yl,2-penten-1-yl, 3-penten-2-yl, 2-methyl-1-buten-3-yl,2-methyl-3-buten-2-yl, 3-methyl-2-buten-1-yl, 1,4-pentadien-3-yl,2-cyclopenten-1-yl, 2-cyclohexen-1-yl, 3-cyclohexen-1-yl,2,4-cyclohexadien-1-yl, 1-p-menthen-8-yl, 4(10)-thujen-10-yl,2-norbornen-1-yl, 2,5-norbornadien-1-yl,7,7-dimethyl-2,4-norcaradien-3-yl and the various isomers of hexenyl,octenyl, nonenyl, decenyl and dodecenyl.

C₂-C₄Alkylene is, for example, 1,2-ethylene, 1,2-propylene,1,3-propylene, 1,2-butylene, 1,3-butylene, 2,3-butylene, 1,4-butyleneand 2-methyl-1,2-propylene. C₅-C₁₂Alkylene is, for example, an isomer ofpentylene, hexylene, octylene, decylene or dodecylene.

C₁-C₁₂Alkoxy is O—C₁-C₁₂alkyl, preferably O—C₁-C₄alkyl.

C₆-C₁₂Aryloxy is O—C₁-C₁₂aryl, for example phenoxy or naphthyloxy,preferably phenoxy.

C₁-C₁₂Alkylthio is S—C₁-C₁₂alkyl, preferably S—C₁-C₄alkyl.

C₆-C₁₂Arylthio is S—C₆-C₁₂aryl, for example phenylthio or naphthylthio,preferably phenylthio.

C₂-C₂₄-Dialkylamino is N(alkyl₁)(alkyl₂), the sum of the carbon atoms inthe two groups alkyl₁ and alkyl₂ being from 2 to 24, preferablyN(C₁-C₄alkyl)-C₁-C₄alkyl.

C₇-C₂₄Alkylarylamino is N(alkyl₁)(aryl₂), the sum of the carbon atoms inthe two groups alkyl₁ and aryl₂ being from 7 to 24, for examplemethylphenylamino, ethylnaphthylamino or butylphenanthrylamino,preferably methylphenylamino or ethylphenylamino.

C₁₂-C₂₄-Diarylamino is N(aryl₁)(aryl₂), the sum of the carbon atoms inthe two groups aryl₁ and aryl₂ being from 12 to 24, for examplediphenylamino or phenylnaphthylamino, preferably diphenylamino.

Halogen is chlorine, bromine, fluorine or iodine, preferably fluorine orchlorine, especially chlorine.

Preference is given to a method which comprises

a) adding the porous SiO_(z) particles to a solution of a latentpigment,b) precipitating the latent pigment onto the carrier particles, andc) subsequently converting the latent pigment to the pigment(PCT/EP03/10968).

In a preferred embodiment, the latent pigment, for example

is first completely dissolved in an organic solvent, for example amixture of THF and ethanol, at a temperature from 20° C. up to theboiling point of the solvent. The solvent is then added to a previouslyprepared suspension of the porous SiO_(z) particles, in an organicsolvent, for example ethanol, and stirred at a temperature from 20° C.up to the boiling point of the solvent for from 5 to 60 min. Then,within a period of from 10 to 120 min., with vigorous stirring, thesolvent in which the latent pigment has poor solubility, normally water,is slowly added dropwise to the mixture, whereupon the latent pigment isdeposited onto the carrier particles. Stirring is carried out for afurther 10 to 120 minutes. The carrier particles coloured with thelatent pigment are then filtered off, washed and dried.

Conversion of the pigment precursor into its pigmentary form is carriedout by means of fragmentation under known conditions, for examplethermally, optionally in the presence of an additional catalyst, forexample the catalysts described in WO00/36210.

If the pores of the flakes are filled with organic pigment,interferences are observed, if the thickness of the flakes is in therange of from 200 to 500 nm, whereby the color of the pigment can bemodified. If the pore size is smaller than 50 nm, the flakes loaded withthe organic pigment are transparent.

The pores of the flakes can also be filled with inorganic pigments, suchas, for example iron oxides, whereby black, yellow or red colors can beformed. Such flakes can be easily dispersed in organic binders.Dependent on the phase of the iron oxide the SiO_(z) flakes loaded withiron oxide can be magnetic. SiO_(z) flakes loaded with magnetic ironoxide, which have additionally been coated with Ag, can, for example beused for electromagnetic shielding.

Furthermore, the porous SiO_(z) flakes, especially the pores of theflakes, can be covered with carbon, such as diamond-like carbon andamorphous carbon, by means of plasma supported deposition from the vaporphase by Plasma Enhanced Chemical Vapor Deposition (PECVD) or by meansof magnetron sputtering (see, for example, U.S. Pat. No. 6,524,381). Theplasma deposition can, for example, be carried out at room temperatureand a pressure of 1 to 50 10³ Pa making using argon as buffer or inertgas and methane, ethene or acetylene as process gas and optionally inthe presence of a doping gas may occur.

Consequently, the present invention also relates to plane-parallelstructures (pigments) based on porous SiO_(z) substrates coated withcarbon, especially diamond-like carbon. If the carbon is not onlypresent in the pores, but also forms a layer, the thickness of thecarbon layer is in the range of 10 to 150 nm.

Furthermore, the porous SiO_(z) flakes, especially the pores of theflakes, can be filled with oxides of the elements titanium, iron, orzirconium.

The pores of the SiO_(z) flakes show in this case a pore diameter ofless than 30 nm, whereby highly translucent products with highabsorption and reflection in the ultraviolet region are received. Theparticles can be obtained, for example, by adding a titaniumtetrachloride solution to an aqueous dispersion of the SiO_(z) flakes,separating the coated SiO_(z) flakes, drying them and optionallycalcinating them. It also exists the possibility, to produce nano TiO₂of the rutile type with particle sizes between 1 to 50 nm by hydrolysisof TiCl₄ with hydrochloric acid at temperatures between 0 to 60° C. (R.J. Nussbaumer, W. Caseri, T. Tervoort and P. Smith, Journal ofNanoparticle Research 2002, 4, 319-323; Anpo et al. J. Phys. Chem. 1987,91, 4305. It also exists the possibility, to produce nano TiO₂ of theanastase type with particle sizes between 10 to 40 nm by hydrolysis ofTi(OiPr)₄ (=titanium tetraisopropoxide) with water at 0 to 50° C. andsubsequent removal of the formed isopropanol at temperatures between 50to 100° C. and low vacuum (ca. 200 Torr) (crystallite size: <10 nm) (K.I. Gnanasekar et al. Journal of Materials Research 2002, 17(6),1507-1512). A solution of titanic acid, produced from TiCl₄ byhydrolysis with ammonium hydroxide and subsequent oxidation with H₂O₂can be added to a diluted solution of the SiO_(z) flakes. By heating at100 to 250° C., nano TiO₂ particles of the anatase type resultspontaneously from this solution with particle sizes of approx. 10 nm(H. Ichinose, M. Terasaki and H. Katsuki, Journal of the Ceramic Societyof Japan, Int. Edition 1996, 104(8), 715-718). Such solutions anddispersion are meanwhile also commercially available (Kon Corporation,91-115 Miyano Yamauchi, Kishimagun Saga-prefecture, Japan 849-2305). TheSiO_(z) flakes loaded with oxides of titanium, zirconia and iron can becoated with organic or inorganic compounds in accordance with knownprocedures. TiO₂ coated SiO_(z) flakes can be used in media, where ahigh translucency is important, such as, for example, in varnishes,paints, plastics, or glass, and/or as a sun protective agent incosmetics formulations. Furthermore the coated SiO_(z) flakes can beused for the pigmentation of paints, printing inks, plastics andcoatings (see, for example, EP-A-803550). SiO_(z) flakes coated withTiO₂, especially TiO₂ of the anatase type, can have photocatalyticactivity. Hence, such flakes exhibit self cleaning and disinfectingproperties under exposure to UV radiation. These properties make theflakes a candidate for use in sterilization, sanitation, and remediationapplications.

SiO_(z) flakes covered with TiO₂ in the rutile modification can be usedas highly efficient, translucent, little or hardly photoactive UVabsorbers, e.g. in cosmetics (sun protective cremes), automobile or woodvanish etc. In addition to the UV protection such SiO_(z) flakes alsoincrease the scratch resistance and improve other physical properties,such as the modulus of elasticity.

According to the present invention the term “SiO_(z) flakes coated withTiO₂ (or any other material)”, or “SiO_(z) flakes covered with TiO₂”includes that the whole surface of the SiO_(z) flakes is coated withTiO₂, that the pores or parts of the pores of the SiO_(z) flakes arefilled with TiO₂ and/or that the SiO_(z) flakes are coated at individualpoints with TiO₂.

If colours are desired, the colour effect of the pigments can generallybe adjusted by way of

-   -   the thickness of the TiO₂ layer,    -   the thickness of the intermediate layer and    -   the composition of the intermediate layer.

TiO₂ coated SiO_(y) flakes with 0.70≦y≦1.8, especially 1.1≦y≦1.5 can be,as described in PCT/EP03/50690, first calcined in a non-oxidising gasatmosphere at a temperature of more than 600° C., and the TiO₂ coatedSiO_(y) platelets are then treated, where appropriate, at a temperatureof more than 200° C., preferably more than 400° C. and especially from500 to 1000° C., with air or another oxygen-containing gas.

It is assumed that calcining TiO₂/SiO_(y) in a non-oxidising atmosphereproduces an intermediate layer that causes a change in the refractiveindex. However, the possibility that the intermediate layer is not acontinuous layer and that, rather, only individual regions at theinterface of TiO₂ and SiO_(y) undergo a conversion that causes a changein the refractive index cannot be ruled out. It is further assumed thatthe change in the refractive index is due to the reduction of TiO₂ bySiO_(y). The principle according to the invention is based, therefore,on producing, by reduction of TiO₂ with SiO_(y), an intermediate layerthat causes a change in the refractive index.

TiO₂+SiO_(y)→SiO_(y+b)TiO_(2-b)

If it is not intended to form the intermediate layer, the porous SiO_(y)flakes must be oxidized to SiO₂ before coating with TiO₂. At present, itcan not be excluded, that by heating TiO₂/SiO_(y) particles in anoxygen-free atmosphere, i.e. an argon or helium atmosphere, or in avacuum of less than 13 Pa (10⁻¹ Torr), at a temperature above 400° C.,especially 400 to 1100° C., besides the reduction of TiO₂ by SiO_(y)SiO_(y) also disproportionates in SiO₂ and Si (PCT/EP03/50229).

SiO_(y)→(y/y+a)SiO_(y+a)+(1−(y/y+a))Si

In this disproportion SiO_(y+a) flakes are formed, containing(1−(y/y+a)) Si, wherein 0.70≦y≦0.99 or 1.0≦y≦1.8, 0.05≦a≦1.30,especially 0.05≦a≦1.0, and the sum y and a is equal or less than 2.SiO_(y+a) is an oxygen enriched silicon suboxide.

If the SiO_(z) flakes are loaded with donated materials, as for exampletin-donated indium oxide, as described, for example in example 5 ofWO02/31060, SiO_(z) flakes with high IR absorbency can be obtained.

If the SiO_(z) flakes are loaded with SnO₂, Sb₂O₃/SnO₂, In₂O₃ orIn₂O₃/SnO₂ SiO_(z) flakes with high IR reflecting power can be obtained(cf. U.S. Pat. No. 4,548,836).

For the production of interference pigments the process according to thepresent invention can be modified in such a manner, that between twomixed layers of material and separating agent further layers of metal,or metal oxide are deposited and/or in case of unsymmetrical layerstructure of the pigment further layers of metal, or metal oxide aredeposited before the mixed layer of material and separating agent.

Hence, the present invention also relates to platelike pigments,comprising a layer of porous material, especially SiO_(z) with0.70≦z≦2.0.

Especially preferred are pigments, comprising

(a) a core of a metal, especially aluminum,(b) optionally a SiO_(z) layer on the core of aluminum and(c) a layer of porous SiO_(z) on the core of aluminum or the SiO_(z)layer, wherein 0.70≦z≦2.0, such as porous SiO_(z)/Al/porous SiO_(z),porous SiO_(z)/SiO_(z)/Al/SiO_(z)/porous SiO_(z), wherein unsymmetricalstructures, such as porous SiO_(z)/Al/SiO_(z), orSiO_(z)/Al/SiO_(z)/porous SiO_(z), are less preferred.

The metal is preferably selected from Ag, Al, Au, Cu, Cr, Ge, Mo, Ni,Si, Ti, or the alloys thereof. Most preferred is Al.

The layer of porous SiO_(z) (c) contains preferably an inorganic ororganic coloring agent, such as a dye or an inorganic or organicpigment, especially an organic pigment.

In said embodiment pigments are particularly preferred, which comprise(in this order)

(c1) a layer of porous SiO_(z) (thickness=40 to 60 nm, especially ca. 50nm),(b1) a SiO_(z) layer (thickness=20 to 500 nm),(a) a core of aluminum (thickness=40 to 60 nm, especially ca. 50 nm),(b2) a SiO_(z) layer (thickness=20 to 500 nm) and(c2) a layer of porous SiO_(z) (thickness=40 to 60 nm, especially ca. 50nm), wherein 1.40≦z≦2.0, especially 2.0, wherein layers (c1) and (c2)contains a dye or an inorganic or organic pigment, especially an organicpigment. Said pigments can optionally be coated with a protective layerof a material of low index of refraction, especially SiO₂. The pigmentsare characterized by a high chroma, which is caused by the combinationof the absorption of the pigments incorporated in the porous layers andthe interference colors of the pigments.

Further especially preferred pigments comprise (in this order)

(a) a layer of porous SiO_(z);(b) a SiO_(z) layer and(c) optionally a layer of porous SiO_(z), wherein 0.70≦z≦2.0, which arepreferably coated by a wet-chemical method with a metal oxide having ahigh index of refraction, especially TiO₂. That is, the core of thepigments is formed by porous SiO_(z)/SiO_(z) or porousSiO_(z)/SiO_(z)/porous SiO_(z) flakes.

The porous SiO_(z)/SiO_(z) flakes are prepared by a PVD processcomprising the steps:

a) vapor-deposition of a separating agent onto a (movable) carrier toproduce a separating agent layer,b) vapor-deposition of a mixed layer of SiO_(y) and separating agentonto the separating agent layer,c) vapor-deposition of an SiO_(y) layer onto the mixed layer, wherein0.70≦y≦1.80,d) optionally vapor-deposition of a mixed layer of SiO_(y) andseparating agent onto the SiO_(y) layer,e) dissolution of the separating agent layer in a solvent, andf) separation of the obtained porous SiO_(z)/SiO_(z) flakes from thesolvent.

The pores of the porous layer can be filled with an organic pigment asdescribed above, whereby it is possible to combine interference colorswith the absorption of the pigments. Dependent on the layer thickness ofthe SiO_(z) layer very high saturations can be obtained.

The porous SiO_(z) flakes, especially SiO₂ flakes, whose effectiverefractive index is lower than that of SiO₂ (n=1.46) and is in the rangeof from 1.25-1.40 can be employed as substrates for interferencepigments instead of SiO₂ flakes, or layered silicate flakes (e.g. mica,montmorillonite, saponite etc.).

Accordingly, the present invention is also directed to pigments, whoseparticles generally have a length of from 1 μm to 5 mm, a width of from1 μm to 2 mm, and a thickness of from 50 nm to 1.5 μm, and a ratio oflength to thickness of at least 2:1, wherein the particles have a coreof porous SiO_(z), porous SiO_(z)/SiO_(z), SiO_(z)/porousSiO_(z)/SiO_(z) or porous SiO_(z)/SiO_(z)/porous SiO_(z) with0.70≦z≦2.0, especially 1.1≦z≦2.0, very especially 1.4≦z≦2.0 having twosubstantially parallel faces, the distance between which is the shortestaxis of the core, comprising (a) a metal oxide of high index ofrefraction; or

pigments, whose particles generally have a length of from 1 μm to 5 mm,a width of from 1 μm to 2 mm, and a thickness of from 50 nm to 1.5 μm,and a ratio of length to thickness of at least 2:1, wherein theparticles have a core of porous SiO_(z), porous SiO_(z)/SiO_(z),SiO_(z)/porous SiO_(z)/SiO_(z) or porous SiO_(z)/SiO_(z)/porous SiO_(z)with 0.70≦z≦2.0, especially 1.1≦z≦2.0, very especially 1.4≦z≦2.0 havingtwo substantially parallel faces, the distance between which is theshortest axis of the core, comprising(a) a thin semitransparent metal layer.

Suitable metals for the semi-transparent metal layer are, for example,Cr, Ti, Mo, W, Al, Cu, Ag, Au, or Ni. The semi-transparent metal layerhas typically a thickness of between 5 and 25 nm, especially between 5and 15 nm. The SiO_(y) substrates can have a metal layer only on oneparallel face, but preferably the metal layer is present on bothparallel faces of the substrate.

Alternatively the metal layer can be obtained by wet chemical coating orby chemical vapor deposition, for example, gas phase deposition of metalcarbonyls. The substrate is suspended in an aqueous and/or organicsolvent containing medium in the presence of a metal compound and isdeposited onto the substrate by addition of a reducing agent. The metalcompound is, for example, silver nitrate or nickel acetyl acetonate(WO03/37993).

According to U.S. Pat. No. 3,536,520 nickel chloride can be used asmetal compound and hypophosphite can be used as reducing agent.According to EP-A-353544 the following compounds can be used as reducingagents for the wet chemical coating: aldehydes (formaldehyde,acetaldehyde, benzalaldehyde), ketones (acetone), carbonic acids andsalts thereof (tartaric acid, ascorbinic acid), reductones(isoascorbinic acid, triosereductone, reductine acid), and reducingsugars (glucose).

If semi-transparent metal layers are desired, the thickness of the metallayer is generally between 5 and 25 nm, especially between 5 and 15 nm.

If pigments with metallic appearance (=opaque metal layer) are desired,the thickness of the metal layer is >25 nm to 100 nm, preferably 30 to50 nm. If pigments with colored metal effects are desired, additionallayers of colored or colorless metal oxides, metal nitrides, metalsulfides and/or metals can be deposited. These layers are transparent orsemi-transparent. It is preferred that layers of high index ofrefraction and layers of low index of refraction alternate or that onelayer is present, wherein within the layer the index of refraction isgradually changing. It is possible for the weathering resistance to beincreased by means of an additional coating, which at the same timecauses an optimal adaption to the binder system (EP-A-268918 andEP-A-632109). Porous SiO_(z) flakes coated, for example, with Ag, or Niare electrically conductive and can be used, for example, in themetallisation of hybrid microcircuits, solar cells, superconductingcircuits and large area electronic structures by, for example, ink jetprinting.

In one preferred embodiment of the present invention, the interferencepigments comprise materials having a “high” index of refraction, whichis defined herein as an index of refraction of greater than about 1.65,and optionally materials having a “low” index of refraction, which isdefined herein as an index of refraction of about 1.65 or less. Various(dielectric) materials that can be utilized including inorganicmaterials such as metal oxides, metal suboxides, metal fluorides, metaloxyhalides, metal sulfides, metal chalcogenides, metal nitrides, metaloxynitrides, metal carbides, combinations thereof, and the like, as wellas organic dielectric materials. These materials are readily availableand easily applied by physical, or chemical vapor deposition processes,or by wet chemical coating processes.

In an especially preferred embodiment, the interference pigments on thebasis of the porous silicon oxide substrate (includes porous SiO_(z),porous SiO_(z)/SiO_(z), SiO_(z)/porous SiO_(z)/SiO_(z) as well as porousSiO_(z)/SiO_(z)/porous SiO_(z)) comprises a further layer of adielectric material having a “high” refractive index, that is to say arefractive index greater than about 1.65, preferably greater than about2.0, most preferred greater than about 2.2, which is applied to theentire surface of the silicon/silicon oxide substrate. Examples of sucha dielectric material are zinc sulfide (ZnS), zinc oxide (ZnO),zirconium oxide (ZrO₂), titanium dioxide (TiO₂), carbon, indium oxide(In₂O₃), indium tin oxide (ITO), tantalum pentoxide (Ta₂O₅), chromiumoxide (Cr₂O₃), cerium oxide (CeO₂), yttrium oxide (Y₂O₃), europium oxide(Eu₂O₃), iron oxides such as iron(II)/iron(III) oxide (Fe₃O₄) andiron(III) oxide (Fe₂O₃), hafnium nitride (HfN), hafnium carbide (HfC),hafnium oxide (HfO₂), lanthanum oxide (La₂O₃), magnesium oxide (MgO),neodymium oxide (Nd₂O₃), praseodymium oxide (Pr₆O₁₁), samarium oxide(Sm₂O₃), antimony trioxide (Sb₂O₃), silicon monoxides (SiO), seleniumtrioxide (Se₂O₃), tin oxide (SnO₂), tungsten trioxide (WO₃) orcombinations thereof. The dielectric material is preferably a metaloxide. It being possible for the metal oxide to be a single oxide or amixture of oxides, with or without absorbing properties, for example,TiO₂, ZrO₂, Fe₂O₃, Fe₃O₄, Cr₂O₃ or ZnO, with TiO₂ being especiallypreferred.

It is possible to obtain pigments that are more intense in colour andmore transparent by applying, on top of the TiO₂ layer, a metal oxide oflow refractive index, such as SiO₂, Al₂O₃, AlOOH, B₂O₃ or a mixturethereof, preferably SiO₂, and optionally applying a further TiO₂ layeron top of the latter layer (EP-A-892832, EP-A-753545, WO93/08237,WO98/53011, WO9812266, WO9838254, WO99/20695, WO00/42111, andEP-A-1213330). Nonlimiting examples of suitable low index dielectricmaterials that can be used include silicon dioxide (SiO₂), aluminumoxide (Al₂O₃), and metal fluorides such as magnesium fluoride (MgF₂),aluminum fluoride (AlF₃), cerium fluoride (CeF₃), lanthanum fluoride(LaF₃), sodium aluminum fluorides (e.g., Na₃AlF₆ or Na₅Al₃F₁₄),neodymium fluoride (NdF₃), samarium fluoride (SmF₃), barium fluoride(BaF₂), calcium fluoride (CaF₂), lithium fluoride (LiF), combinationsthereof, or any other low index material having an index of refractionof about 1.65 or less. For example, organic monomers and polymers can beutilized as low index materials, including dienes or alkenes such asacrylates (e.g., methacrylate), polymers of perfluoroalkenes,polytetrafluoroethylene (TEFLON), polymers of fluorinated ethylenepropylene (FEP), parylene, p-xylene, combinations thereof, and the like.Additionally, the foregoing materials include evaporated, condensed andcross-linked transparent acrylate layers, which may be deposited bymethods described in U.S. Pat. No. 5,877,895, the disclosure of which isincorporated herein by reference.

Accordingly, preferred interference pigments comprise besides (a) ametal oxide of high refractive index and in addition (b) a metal oxide,or a nonmetal oxide of low refractive index, wherein the difference ofthe refractive indices is at least 0.1.

Pigments on the basis of porous silicon oxide (SiO_(z)) substrates,which have been coated by a wet chemical method, in the indicated orderare particularly preferred:

TiO₂ (substrate: silicon oxide; layer: TiO₂, preferably in the rutilemodification), (SnO₂)TiO₂, Fe₂O₃, Fe₃O₄, TiFe₂O₅, Cr₂O₃, ZrO₂, Sn(Sb)O₂,BiOCl, Al₂O₃, Ce₂S₃, MoS₂, Fe₂O₃.TiO₂ (substrate: silicon oxide; mixedlayer of Fe₂O₃ and TiO₂). TiO₂/Fe₂O₃ (substrate: silicon oxide; firstlayer: TiO₂; second layer: Fe₂O₃), TiO₂/Berlin blau, TiO₂/Cr₂O₃, orTiO₂/FeTiO₃. In general the layer thickness ranges from 1 to 1000 nm,preferably from 1 to 300 nm.

In another particularly preferred embodiment the present inventionrelates to interference pigments containing at least three alternatinglayers of high and low refractive index, such as, for example,TiO₂/SiO₂/TiO₂, (SnO₂)TiO₂/SiO₂TiO₂, TiO₂/SiO₂/TiO₂/SiO₂/TiO₂ orTiO₂/SiO₂/Fe₂O₃: Preferably the layer structure is as follows:

(A) a coating having a refractive index >1.65,(B) a coating having a refractive index ≦1.65,(C) a coating having a refractive index >1.65, and(D) optionally an outer protective layer.

The thickness of the individual layers of high and low refractive indexon the base substrate is essential for the optical properties of thepigment. The thickness of the individual layers, especially metal oxidelayers, depends on the field of use and is generally 10 to 1000 nm,preferably 15 to 800 nm, in particular 20 to 600 nm.

The thickness of layer (A) is 10 to 550 nm, preferably 15 to 400 nm and,in particular, 20 to 350 nm. The thickness of layer (B) is 10 to 1000nm, preferably 20 to 800 nm and, in particular, 30 to 600 nm. Thethickness of layer (C) is ±0 to 550 nm, preferably 15 to 400 nm and, inparticular, 20 to 350 nm.

Particularly suitable materials for layer (A) are metal oxides, metalsulfides, or metal oxide mixtures, such as TiO₂, Fe₂O₃, TiFe₂O₅, Fe₃O₄,BiOCl, CoO, CO₃O₄₁ Cr₂O₃, VO₂, V₂O₃, Sn(Sb)O₂, SnO₂, ZrO₂, irontitanates, iron oxide hydrates, titanium suboxides (reduced titaniumspecies having oxidation states from 2 to <4), bismuth vanadate, cobaltaluminate, and also mixtures or mixed phases of these compounds with oneanother or with other metal oxides. Metal sulfide coatings arepreferably selected from sulfides of tin, silver, lanthanum, rare earthmetals, preferably cerium, chromium, molybdenum, tungsten, iron, cobaltand/or nickel.

Particularly suitable materials for layer (B) are metal oxides or thecorresponding oxide hydrates, such as SiO₂, MgF₂, Al₂O₃, AlOOH, B₂O₃ ora mixture thereof, preferably SiO₂.

Particularly suitable materials for layer (C) are colorless or coloredmetal oxides, such as TiO₂, Fe₂O₃, TiFe₂O₅, Fe₃O₄, BiOCl, CoO, Co₃O₄,Cr₂O₃, VO₂, V₂O₃, Sn(Sb)O₂, SnO₂, ZrO₂, iron titanates, iron oxidehydrates, titanium suboxides (reduced titanium species having oxidationstates from 2 to <4), bismuth vanadate, cobalt aluminate, and alsomixtures or mixed phases of these compounds with one another or withother metal oxides. The TiO₂ layers can additionally contain anabsorbing material, such as carbon, selectively absorbing colorants,selectively absorbing metal cations, can be coated with absorbingmaterial, or can be partially reduced.

Interlayers of absorbing or nonabsorbing materials can be presentbetween layers (A), (B), (C) and (D). The thickness of the interlayersis 1 to 50 nm, preferably 1 to 40 nm and, in particular, 1 to 30 nm.

In this embodiment preferred interference pigments have the followinglayer structure:

porous SiO_(z) TiO₂ SiO₂ TiO₂ porous SiO_(z) TiO₂ SiO₂ Fe₂O₃ porousSiO_(z) TiO₂ SiO₂ TiO₂/Fe₂O₃ porous SiO_(z) TiO₂ SiO₂ (Sn,Sb)O₂ porousSiO_(z) (Sn,Sb)O₂ SiO₂ TiO₂ porous SiO_(z) Fe₂O₃ SiO₂ (Sn,Sb)O₂ porousSiO_(z) TiO₂/Fe₂O₃ SiO₂ TiO₂/Fe₂O₃ porous SiO_(z) TiO₂ SiO₂ MoS₂ porousSiO_(z) TiO₂ SiO₂ Cr₂O₃ porous SiO_(z) Cr₂O₃ SiO₂ TiO₂ porous SiO_(z)Fe₂O₃ SiO₂ TiO₂ porous SiO_(z) TiO₂ Al₂O₃ TiO₂ porous SiO_(z) Fe₂TiO₅SiO₂ TiO₂ porous SiO_(z) TiO₂ SiO₂ Fe₂TiO₅/TiO₂ porous SiO_(z) TiOsuboxides SiO₂ TiO suboxides porous SiO_(z) TiO₂ SiO₂ TiO₂ + SiO₂ +TiO₂ + Prussian Blue porous SiO_(z) TiO₂ SiO₂ TiO₂ + SiO₂ + TiO₂ porousSiO_(z) TiO₂ + SiO₂ + TiO₂ SiO₂ TiO₂ + SiO₂ + TiO₂

The pigments of the present invention are characterized by the preciselydefined thickness and smooth surface of the thin porous SiO_(z) flakes.Instead of the transparent porous SiO_(z) flakes the porous opaque orsemi opaque silicon/silicon oxide flakes can be used as substrate forinterference pigments.

The metal oxide layers can be applied by CVD (chemical vapor deposition)or by wet chemical coating. The metal oxide layers can be obtained bydecomposition of metal carbonyls in the presence of water vapor(relatively low molecular weight metal oxides such as magnetite) or inthe presence of oxygen and, where appropriate, water vapor (e.g. nickeloxide and cobalt oxide). The metal oxide layers are especially appliedby means of oxidative gaseous phase decomposition of metal carbonyls(e.g. iron pentacarbonyl, chromium hexacarbonyl; EP-A-45 851), by meansof hydrolytic gaseous phase decomposition of metal alcoholates (e.g.titanium and zirconium tetra-n- and -iso-propanolate; DE-A-41 40 900) orof metal halides (e.g. titanium tetrachloride; EP-A-338 428), by meansof oxidative decomposition of organyl tin compounds (especially alkyltin compounds such as tetrabutyltin and tetraethyltin, DE-A-44 03 678)or by means of the gaseous phase hydrolysis of organyl silicon compounds(especially di-tert-butoxyacetoxysilane) described in EP-A-668 329, itbeing possible for the coating operation to be carried out in afluidized-bed reactor (EP-A-045 851 and EP-A-106 235).

Chromate- and/or vanadate-containing and also SiO₂-containing metaloxide layers can be applied in accordance with the passivation methodsdescribed in DE-A-42 36 332 and in EP-A-678 561 by means of hydrolyticor oxidative gaseous phase decomposition of oxide-halides of the metals(e.g. CrO₂Cl₂, VOCl₃), especially of phosphorus oxyhalides (e.g. POCl₃),phosphoric and phosphorous acid esters (e.g. di- and tri-methyl and di-and tri-ethyl phosphite) and of amino-group-containing organyl siliconcompounds (e.g. 3-aminopropyl-triethoxy- and -trimethoxy-silane).

Layers of oxides of the metals zirconium, titanium, iron and zinc, oxidehydrates of those metals, iron titanates, titanium suboxides or mixturesthereof are preferably applied by precipitation by a wet chemicalmethod, it being possible, where appropriate, for the metal oxides to bereduced. In the case of the wet chemical coating, the wet chemicalcoating methods developed for the production of pearlescent pigments maybe used; these are described, for example, in DE-A-14 67 468, DE-A-19 59988, DE-A-20 09 566, DE-A-22 14 545, DE-A-22 15 191, DE-A-22 44 298,DE-A-23 13 331, DE-A-25 22 572, DE-A-31 37 808, DE-A-31 37 809, DE-A-3151 343, DE-A-31 51 354, DE-A-31 51 355, DE-A-32 11 602 and DE-A-32 35017, DE 195 99 88, WO 93/08237, WO 98/53001 and WO03/6558.

The metal oxide of high refractive index is preferably TiO₂ and/or ironoxide, and the metal oxide of low refractive index is preferably SiO₂.Layers of TiO₂ can be in the rutile or anastase modification, whereinthe rutile modification is preferred. TiO₂ layers can also be reduced byknown means, for example ammonia, hydrogen, hydrocarbon vapor ormixtures thereof, or metal powders, as described in EP-A-735,114,DE-A-3433657, DE-A4125134, EP-A-332071, EP-A-707,050 or WO93/19131.

For the purpose of coating, the substrate particles are suspended inwater and one or more hydrolysable metal salts are added at a pHsuitable for the hydrolysis, which is so selected that the metal oxidesor metal oxide hydrates are precipitated directly onto the particleswithout subsidiary precipitation occurring. The pH is usually keptconstant by simultaneously metering in a base. The pigments are thenseparated off, washed, dried and, where appropriate, calcinated, itbeing possible to optimise the calcinating temperature with respect tothe coating in question. If desired, after individual coatings have beenapplied, the pigments can be separated off, dried and, whereappropriate, calcinated, and then again re-suspended for the purpose ofprecipitating further layers.

The metal oxide layers are also obtainable, for example, in analogy to amethod described in DE-A-195 01 307, by producing the metal oxide layerby controlled hydrolysis of one or more metal acid esters, whereappropriate in the presence of an organic solvent and a basic catalyst,by means of a sol-gel process. Suitable basic catalysts are, forexample, amines, such as triethylamine, ethylenediamine, tributylamine,dimethylethanolamine and methoxy-propylamine. The organic solvent is awater-miscible organic solvent such as a C₁₋₄alcohol, especiallyisopropanol.

Suitable metal acid esters are selected from alkyl and aryl alcoholates,carboxylates, and carboxyl-radical- or alkyl-radical- oraryl-radical-substituted alkyl alcoholates or carboxylates of vanadium,titanium, zirconium, silicon, aluminum and boron. The use oftriisopropyl aluminate, tetraisopropyl titanate, tetraisopropylzirconate, tetraethyl orthosilicate and triethyl borate is preferred. Inaddition, acetylacetonates and acetoacetylacetonates of theafore-mentioned metals may be used. Preferred examples of that type ofmetal acid ester are zirconium acetylacetonate, aluminumacetylacetonate, titanium acetylacetonate and diisobutyloleylacetoacetylaluminate or diisopropyloleyl acetoacetylacetonate andmixtures of metal acid esters, for example Dynasil® (Hüls), a mixedaluminum/silicon metal acid ester.

As a metal oxide having a high refractive index, titanium dioxide ispreferably used, the method described in U.S. Pat. No. 3,553,001 beingused, in accordance with an embodiment of the present invention, forapplication of the titanium dioxide layers.

An aqueous titanium salt solution is slowly added to a suspension of thematerial being coated, which suspension has been heated to about 50-100°C., especially 70-80° C., and a substantially constant pH value of aboutfrom 0.5 to 5, especially about from 1.2 to 2.5, is maintained bysimultaneously metering in a base such as, for example, aqueous ammoniasolution or aqueous alkali metal hydroxide solution. As soon as thedesired layer thickness of precipitated TiO₂ has been achieved, theaddition of titanium salt solution and base is stopped.

This method, also referred to as the “titration method”, isdistinguished by the fact that an excess of titanium salt is avoided.That is achieved by feeding in for hydrolysis, per unit time, only thatamount which is necessary for even coating with the hydrated TiO₂ andwhich can be taken up per unit time by the available surface of theparticles being coated. In principle, the anatase form of TiO₂ forms onthe surface of the starting pigment. By adding small amounts of SnO₂,however, it is possible to force the rutile structure to be formed. Forexample, as described in WO 93/08237, tin dioxide can be depositedbefore titanium dioxide precipitation and the product coated withtitanium dioxide can be calcined at from 800 to 900° C.

The TiO₂ can optionally be reduced by usual procedures: U.S. Pat. No.4,948,631 (NH₃, 750-850° C.), WO93/19131 (H₂, >900° C.) or DE-A-19843014(solid reduction agent, such as, for example, silicon, >600° C.).

Where appropriate, an SiO₂ (protective) layer can be applied on top ofthe titanium dioxide layer, for which the following method may be used:A soda waterglass solution is metered in to a suspension of the materialbeing coated, which suspension has been heated to about 50-100° C.,especially 70-80° C. The pH is maintained at from 4 to 10, preferablyfrom 6.5 to 8.5, by simultaneously adding 10% hydrochloric acid. Afteraddition of the waterglass solution, stirring is carried out for 30minutes.

It is possible to obtain pigments that are more intense in colour andmore transparent by applying, on top of the TiO₂ layer, a metal oxide of“low” refractive index, that is to say a refractive index smaller thanabout 1.65, such as SiO₂, Al₂O₃, AlOOH, B₂O₃ or a mixture thereofpreferably SiO₂, and applying a further Fe₂O₃ and/or TiO₂ layer on topof the latter layer. Such multi-coated interference pigments comprisinga porous silicon oxide substrate or a porous silicon/silicon oxidesubstrate and alternating metal oxide layers of high and low refractiveindex can be prepared in analogy to the processes described inWO98/53011 and WO99/20695.

It is, in addition, possible to modify the powder colour of the pigmentby applying further layers such as, for example, coloured metal oxidesor Berlin Blue, compounds of transition metals, e.g. Fe, Cu, Ni, Co, Cr,or organic compounds such as dyes or colour lakes.

In addition, the pigment according to the invention can also be coatedwith poorly soluble, firmly adhering, inorganic or organic colourants.Preference is given to the use of colour lakes and, especially, aluminumcolour lakes. For that purpose an aluminum hydroxide layer isprecipitated, which is, in a second step, laked by using a colour lake(DE-A-24 29 762 and DE 29 28 287).

Furthermore, the pigment according to the invention may also have anadditional coating with complex salt pigments, especially cyanoferratecomplexes (EP-A-141 173 and DE-A-23 13 332).

According to DE-A4009567 the pigments according to the invention canalso be coated with organic dyes, especially phthalocyanine or metalphthalocyanine and/or indanthrene dyes. A suspension of the pigment isproduced in a solution of the dye and a solvent is added, in which thedye is insoluble. Furthermore, metal chalcogenides and/or metalchalcogenide hydrates and carbon black can be used for an additionalcoating.

To enhance the weather and light stability the multiplayer silicon oxideflakes can be, depending on the field of application, subjected to asurface treatment. Useful surface treatments are, for example, describedin DE-A-2215191, DE-A-3151354, DE-A-3235017, DE-A-3334598, DE-A-4030727,EP-A-649886, WO97/29059, WO99/57204, and U.S. Pat. No. 5,759,255. Saidsurface treatment might also facilitate the handling of the pigment,especially its incorporation into various application media.

In the case of multilayer pigments, the interference color is determinedby the intensification of certain wavelengths, and if two or more layersin a multilayer pigment have the same optical thickness, the color ofthe reflected light becomes fuller and more intense as the number oflayers increases. In addition to this, it is possible through anappropriate choice of layer thicknesses to achieve a particularly strongvariation of the color as a function of the viewing angle. A pronouncedcolor flop is developed, which may be desirable for the pigmentsaccording to the invention. Hence, the thickness of the individual metaloxide layers independently of their index of refraction is in the rangeof from 20 to 500 nm, especially in the range of from 50 bis 300 nm.

The number and thickness of the layers depends on the desired effect.The desired effects are achieved, if the three layer systemTiO₂/SiO_(z)/TiO₂ is used and the thickness of the individual layers isoptically synchronized to each other. By using optical relative thinTiO₂ and SiO₂ layers (layer thickness <100 nm) pigments can be produced,which have an essentially lower TiO₂ content and a more intense colorand are more transparent as pure TiO₂/mica pigments. By deposition ofthick SiO₂ layers (layer thickness >100 nm) pigments having aparticularly strong variation of the color as a function of the viewingangle are obtained. By deposition of further TiO₂ and SiO₂ layers fivelayer systems or higher layer systems can be obtained, the number oflayers is, however, limited by economic aspects. By using of porousSiO_(z) flakes or porous silicon/silicon oxide flakes of uniformthickness as substrate well defined interference effects can beobtained.

In this case, one receives an interference system by coating thesubstrate with e.g. 3 layers of the above-mentioned structure of 7 thinlayers of a well-defined thickness. The reflection and/or transmissionspectrum of such a pigment shows finer and exactly adjustable structuresas the spectrum of a corresponding pigment, that is based on a substratewith a broad distribution of thickness, e.g. mica.

These pigments already show with extremely thin TiO₂ layers (layerthickness <50 nm) strong interference colors. The angular dependence ofthe interference color is also especially distinct.

The (effect) pigments according to the invention are characterised by ahigh gloss and a high uniformity of thickness, whereby a high colorpurity and a high color strength is achieved.

The (effect) pigments according to the invention can be used for allcustomary purposes, for example for colouring polymers in the mass,coatings (including effect finishes, including those for the automotivesector) and printing inks (including offset printing, intaglio printing,bronzing and flexographic printing), and also, for example, forapplications in cosmetics, in ink-jet printing, for dyeing textiles,glazes for ceramics and glass as well as laser marking of papers andplastics. Such applications are known from reference works, for example“Industrielle Organische Pigmente” (W. Herbst and K. Hunger, VCHVerlagsgesellschaft mbH, Weinheim/New York, 2nd, completely revisededition, 1995).

A process for preparing a matrix material loaded with nanoparticlesforms a further subject of the present invention. The process comprises

a) vapor-deposition of a separating agent onto a carrier to produce aseparating agent layer,b) then the simultaneous vapor-deposition of a matrix material and amaterial forming the nanoparticles onto the separating agent layer (a),c) the separation of the material from the separating agent, inparticular by dissolving the separating agent in a solvent, andd) optionally separation of the matrix material charged with thenanoparticles from the solvent.

The process is carried out fundamentally as the above described process,except that the material forming the matrix and the material forming thenanoparticles is evaporated instead of the material and the separatingagent.

In principal, any material can be used as matrix material ornanoparticles forming material which can be evaporated under highvacuum. Preferably, metal oxides and non-metal oxides as well asmonomers, oligomers, or polymers are used as matrix materials, which areessentially transparent in the visible region. Advantageously therefractive index of the material loaded with the nanoparticles issimilar to the material, in which the material loaded with thenanoparticles is incorporated (for example, coatings, paints, etc.), inorder to reduce scattering of light of the material loaded with thenanoparticles. The refractive index of the material charged with thenanoparticles can differ insignificantly, especially by not more than0.3 units, from the refractive index of the material, in which thematerial charged with the nanoparticles is incorporated.

In a preferred embodiment of the present invention the matrix materialis a nonmetal oxide, especially transparent SiO_(z) with 1.4≦z≦2.0. Suchmatrix materials are especially suitable as additive inabrasion-resistant (scratch resistant) coatings, since the productremains invisible even in a surface coating having the clarity of water,because the refractive indices are almost the same. The functionality ofthe SiO_(z) flakes is determined by the nanoparticles incorporatedtherein.

The flakes produced in accordance with the process of the present mayalso be further treated at their surface in accordance with knownmethods in order to obtain hydrophobic, hydrophilic or antistaticproperties or to allow coupling of organic compounds. The plane-parallelstructures become oriented parallel to the surface of the coated objectand, after subsequent treatment described hereinbelow, form a hard layerclose to the surface of the surface coating.

In another preferred embodiment the matrix material is a component of ahigh molecular weight organic material, especially a paint, a printingink, or a coating, which are vaporizable in vacuo and can be processedto flakes by the inventive process. Suitable matrix materials should bevaporizable without decomposition and should not react with thenanoparticles incorporated in the matrix. Preferably, the matrixmaterials should be capable of being used in a continuous PVD method andespecially of being vaporised in an industrial context in amounts ofmore than 1 kg/h with little thermal decomposition. The amounts ofnon-condensable cracked gases that form should be substantially lessthan the capacities of the high-vacuum pumps customarily used for suchmethods. In said embodiment the matrix material is preferably a solidmonomer, macromonomer, oligomer or polymer, which is vaporizable invacuo and is a usual component of a high weight molecular organicmaterial, especially a coating, a paint, or a printing ink. Monomers,for example, acrylate monomers and/or oligomers, can optionally bepolymerised thermically or by radiation with electrons and/or light(see, for example, U.S. Pat. No. 5,440,446 and WO98/38255).

Examples of evaporable polymers are polyacrylic acid, polymethacrylicacid, copolymers of acrylic acid and methacrylic acid, copolymers ofbenzylacrylate and acrylic acid, copolymers of benzylacrylate andmethacrylic acid, copolymers of benzylmethacrylate and acrylic acid,copolymers of benzylmethacrylate and methacrylic acid, copolymers ofstyrene and acrylic acid, copolymers of styrene and methacrylic acid,copolymers of phenethylacrylate and acrylic acid, copolymers ofphenethylacrylate and -methacrylat, copolymers of phenethylmethacrylatand acrylic acid and copolymers of phenethylmethacrylat and methacrylicacid, or mixtures thereof. Homopolymers or copolymers are preferredwhich contain repeating units derived from acrylic acid or methacrylicacid, such as polyacrylic acid, polymethacrylic acid, copolymers ofacrylic acid and methacrylic acid, copolymers of benzylacrylate andacrylic acid, copolymers of benzylmethacrylate and acrylic acid,copolymers of benzylmethacrylate and methacrylic acid, copolymers ofstyrene and acrylic acid, copolymers of styrene and methacrylic acid,copolymers of phenethylacrylate and acrylic acid, copolymers ofphenethylacrylate and methacrylic acid, copolymers ofphenethylmethacrylate and acrylic acid and copolymers ofphenethylmethacrylate and methacrylate (see, for example, DE-A-2706392).

In the two embodiments mentioned above the nanoparticles formingmaterial is preferably an organic pigment or an additive for plastics,paints, coatings, printing inks, or cosmetics, as for example, a UVabsorber, or a metal, in particular aluminum, silicon or a noble metal,as silver, gold, palladium, or platinum.

Pigment nanoparticles incorporated in oligomers or polymers can be addedas transparent pigments to a high molecular organic material, inparticular a paint, without a costly dispersion step, for example, in aball mill (so-called stirin or “easy dispersable” pigments).

The transparent pigments can be, in particular, used for the preparationof effect varnishes, wood varnishes and for pigmenting transparentplastics.

In another preferred embodiment of the present invention SiO_(y) asmatrix material and TiO as material forming the nanoparticles arevaporized by evaporators heated inductively and evaporators heated withelectron beams, respectively. After usual work-up TiO nanoparticlesincorporated in a SiO_(y) matrix are obtained, which can be oxidised inan oxygen containing atmosphere at a temperature above 200° C., wherebytitanium oxide nanoparticles incorporated in a SiO_(z) matrix can beobtained. As described above such particles can be used as highlyefficient, transparent, low or hardly photoactive UV absorber.

Luminescent materials, such as, for example, the luminescent materialsdescribed in WO02/31060 can also be used as the material forming thenanoparticles. In particular the vaporizable complexes of the formula

described in EP-A-801652, can be used, wherein

M is Eu, Tb, Dy, or Sm;

R₂ is hydrogen, or a C₁-C₆alkyl group andR₁ and R₃ are independently of each other a phenyl group, hydrogen, or aC₁-C₆alkyl group, and L is p-N,N-dimethylaminopyridine,N-methylimidazole, or p-methoxypyridine-N-oxide.

In a further embodiment the present invention relates to platelikeSiO_(y+a) particles (matrix material), containing (1−y/y+a) silicon(nanoparticles), wherein 0.70≦y≦1.8, especially 1.0≦y≦1.8, 0.05≦a≦1.30,and the sum of y and a is smaller or equal to 2.

In this case the matrix material and the material forming thenanoparticles is SiO_(y) with 0.70≦y≦1.8. SiO_(y+a) flakes, especiallySiO₂ flakes containing (1−y/y+a) Si nanoparticles can be obtained byheating SiO_(y) particles in an oxygen-free atmosphere, i.e. an argon orhelium atmosphere or in a vacuum of less than 13 Pa (10⁻¹ Torr), at atemperature above 400° C., especially 400 to 1100° C.

It is assumed that by heating SiO_(y) particles in an oxygen-freeatmosphere, SiO_(y) disproportionates in SiO₂ and Si:

SiO_(y)→(y/y+a)SiO_(y+a)+(1−(1−y/y+a)Si

In this disproportion SiO_(y+a) flakes are formed, containing(1−(y/y+a)) Si, wherein 0.70≦y≦1.8, especially 0.70≦y≦0.99 or 1≦y≦1.8,0.05≦a≦1.30, and the sum y and a is equal or less than 2. SiO_(y+a) isan oxygen enriched silicon suboxide. The complete conversion of SiO_(y)in Si and SiO₂ is preferred:

SiO_(y)→(y/2)SiO₂+(1−(y/2))Si

In the temperature range of from 400 to 900° C. the formed silicon isamorph. In the temperature range of from 900 to 1100° C. siliconcrystallites are formed. The average crystallite size is in the range offrom 1 to 20 nm, especially 2 to 10 nm. The size is on the one handdependent on the temperature. That is, at 1100° C. larger crystallitesthan at 900° C. are formed. On the other hand a clear tendency for theformation of smaller crystallites is found, the higher the oxygen levelof the SiO_(y) is. Depending on the preparation the Si containing,plane-parallel SiO_(y+a) particles, especially SiO₂ particles can showphotoluminescence.

The silicon nanoparticles containing SiO_(y) flakes are obtained by theprocess described above, wherein in step b) only one material, namelySiO_(y), is evaporated.

The silicon nanoparticles containing SiO_(y+a) flakes can, for example,be used as substrate for effect pigments. Accordingly, a further subjectof the present invention is formed by platelike pigments, comprising aSiO_(y+a) layer containing silicon nanoparticles, wherein the SiO_(y+a)layer preferably forms the core of the pigment.

The further layers necessary for interferences can be deposited inaccordance with usual procedures known for effect pigments with micaand/or SiO₂ core, which have been described in more detail above bymeans of the porous SiO_(z) flakes.

Metallic or non-metallic, inorganic platelet-shaped particles orpigments are effect pigments, (especially metal effect pigments orinterference pigments), that is to say, pigments that, besides impartingcolour to an application medium, impart additional properties, forexample angle dependency of the colour (flop), lustre (not surfacegloss) or texture. On metal effect pigments, substantially orientedreflection occurs at directionally oriented pigment particles. In thecase of interference pigments, the colour-imparting effect is due to thephenomenon of interference of light in thin, highly refractive layers.

The (effect) pigments according to the invention can be used for allcustomary purposes, for example for colouring polymers in the mass,coatings (including effect finishes, including those for the automotivesector) and printing inks (including offset printing, intaglio printing,bronzing and flexographic printing; see, for example, PCT/EP03/50690),and also, for example, for applications in cosmetics (see, for example,PCT/EP03/09269), in ink-jet printing (see, for example, PCT/EP03/50690),for dyeing textiles (see, for example, PCT/EP03/11188), glazes forceramics and glass as well as laser marking of papers and plastics. Suchapplications are known from reference works, for example “IndustrielleOrganische Pigmente” (W. Herbst and K. Hunger, VCH VerlagsgesellschaftmbH, Weinheim/New York, 2nd, completely revised edition, 1995).

When the interference pigments are goniochromatic and result inbrilliant, highly saturated (lustrous) colours, they are suitable forcombination with conventional, transparent pigments, for example organicpigments such as, for example, diketopyrrolopyrroles, quinacridones,dioxazines, perylenes, isoindolinones etc., it being possible for thetransparent pigment to have a similar colour to the effect pigment.Especially interesting combination effects are obtained, however, inanalogy to, for example, EP-A-388 932 or EP-A-402 943, when the colourof the transparent pigment and that of the effect pigment arecomplementary. The pigments according to the invention can be used withexcellent results for pigmenting high molecular weight organic material.

The high molecular weight organic material for the pigmenting of whichthe pigments or pigment compositions according to the invention may beused may be of natural or synthetic origin. High molecular weightorganic materials usually have molecular weights of about from 10³ to10⁸ g/mol or even more. They may be, for example, natural resins, dryingoils, rubber or casein, or natural substances derived therefrom, such aschlorinated rubber, oil-modified alkyd resins, viscose, cellulose ethersor esters, such as ethylcellulose, cellulose acetate, cellulosepropionate, cellulose acetobutyrate or nitrocellulose, but especiallytotally synthetic organic polymers (thermosetting plastics andthermoplastics), as are obtained by polymerisation, polycondensation orpolyaddition. From the class of the polymerisation resins there may bementioned, especially, polyolefins, such as polyethylene, polypropyleneor polyisobutylene, and also substituted polyolefins, such aspolymerisation products of vinyl chloride, vinyl acetate, styrene,acrylonitrile, acrylic acid esters, methacrylic acid esters orbutadiene, and also copolymerisation products of the said monomers, suchas especially ABS or EVA.

From the series of the polyaddition resins and polycondensation resinsthere may be mentioned, for example, condensation products offormaldehyde with phenols, so-called phenoplasts, and condensationproducts of formaldehyde with urea, thiourea or melamine, so-calledaminoplasts, and the polyesters used as surface-coating resins, eithersaturated, such as alkyd resins, or unsaturated, such as maleate resins;also linear polyesters and polyamides, polyurethanes or silicones. Thesaid high molecular weight compounds may be present singly or inmixtures, in the form of plastic masses or melts. They may also bepresent in the form of their monomers or in the polymerised state indissolved form as film-formers or binders for coatings or printing inks,such as, for example, boiled linseed oil, nitrocellulose, alkyd resins,melamine resins and urea-formaldehyde resins or acrylic resins.

Depending on the intended purpose, it has proved advantageous to use theeffect pigments according to the invention as toners or in the form ofpreparations. Depending on the conditioning method or intendedapplication, it may be advantageous to add certain amounts oftexture-improving agents to the effect pigment before or after theconditioning process, provided that this has no adverse effect on use ofthe effect pigments for colouring high molecular weight organicmaterials, especially polyethylene. Suitable agents are, especially,fatty acids containing at least 18 carbon atoms, for example stearic orbehenic acid, or amides or metal salts thereof, especially magnesiumsalts, and also plasticizers, waxes, resin acids, such as abietic acid,rosin soap, alkylphenols or aliphatic alcohols, such as stearyl alcohol,or aliphatic 1,2-dihydroxy compounds containing from 8 to 22 carbonatoms, such as 1,2-dodecanediol, and also modified colophonium maleateresins or fumaric acid colophonium resins. The texture-improving agentsare added in amounts of preferably from 0.1 to 30% by weight, especiallyfrom 2 to 15% by weight, based on the end product. The (effect) pigmentsaccording to the invention can be added in any tinctorially effectiveamount to the high molecular weight organic material being pigmented. Apigmented substance composition comprising a high molecular weightorganic material and from 0.01 to 80% by weight, preferably from 0.1 to30% by weight, based on the high molecular weight organic material, ofan pigment according to the invention is advantageous. Concentrations offrom 1 to 20% by weight, especially of about 10% by weight, can often beused in practice.

High concentrations, for example those above 30% by weight, are usuallyin the form of concentrates (“masterbatches”) which can be used ascolorants for producing pigmented materials having a relatively lowpigment content, the pigments according to the invention having anextraordinarily low viscosity in customary formulations so that they canstill be processed well.

For the purpose of pigmenting organic materials, the effect pigmentsaccording to the invention may be used singly. It is, however, alsopossible, in order to achieve different hues or colour effects, to addany desired amounts of other colour-imparting constituents, such aswhite, coloured, black or effect pigments, to the high molecular weightorganic substances in addition to the effect pigments according to theinvention. When coloured pigments are used in admixture with the effectpigments according to the invention, the total amount is preferably from0.1 to 10% by weight, based on the high molecular weight organicmaterial. Especially high goniochromicity is provided by the preferredcombination of an effect pigment according to the invention with acoloured pigment of another colour, especially of a complementarycolour, with colorations made using the effect pigment and colorationsmade using the coloured pigment having, at a measurement angle of 10°, adifference in hue (ΔH*) of from 20 to 340, especially from 150 to 210.

Preferably, the effect pigments according to the invention are combinedwith transparent coloured pigments, it being possible for thetransparent coloured pigments to be present either in the same medium asthe effect pigments according to the invention or in a neighbouringmedium. An example of an arrangement in which the effect pigment and thecoloured pigment are advantageously present in neighbouring media is amulti-layer effect coating.

The pigmenting of high molecular weight organic substances with thepigments according to the invention is carried out, for example, byadmixing such a pigment, where appropriate in the form of a masterbatch,with the substrates using roll mills or mixing or grinding apparatuses.The pigmented material is then brought into the desired final form usingmethods known per se, such as calendering, compression moulding,extrusion, coating, pouring or injection moulding. Any additivescustomary in the plastics industry, such as plasticizers, fillers orstabilisers, can be added to the polymer, in customary amounts, beforeor after incorporation of the pigment. In particular, in order toproduce non-rigid shaped articles or to reduce their brittleness, it isdesirable to add plasticizers, for example esters of phosphoric acid,phthalic acid or sebacic acid, to the high molecular weight compoundsprior to shaping.

For pigmenting coatings and printing inks, the high molecular weightorganic materials and the effect pigments according to the invention,where appropriate together with customary additives such as, forexample, fillers, other pigments, siccatives or plasticizers, are finelydispersed or dissolved in the same organic solvent or solvent mixture,it being possible for the individual components to be dissolved ordispersed separately or for a number of components to be dissolved ordispersed together, and only thereafter for all the components to bebrought together.

Dispersing an effect pigment according to the invention in the highmolecular weight organic material being pigmented, and processing apigment composition according to the invention, are preferably carriedout subject to conditions under which only relatively weak shear forcesoccur so that the effect pigment is not broken up into smaller portions.

Plastics comprising the pigment of the invention in amounts of 0.1 to50% by weight, in particular 0.5 to 7% by weight. In the coating sector,the pigments of the invention are employed in amounts of 0.1 to 10% byweight. In the pigmentation of binder systems, for example for paintsand printing inks for intaglio, offset or screen printing, the pigmentis incorporated into the printing ink in amounts of 0.1 to 50% byweight, preferably 5 to 30% by weight and in particular 8 to 15% byweight.

The colorations obtained, for example in plastics, coatings or printinginks, especially in coatings or printing inks, more especially incoatings, are distinguished by excellent properties, especially byextremely high saturation, outstanding fastness properties, high colorpurity and high goniochromicity.

When the high molecular weight material being pigmented is a coating, itis especially a specialty coating, very especially an automotive finish.

The effect pigments according to the invention are also suitable formaking-up the lips or the skin and for colouring the hair or the nails.

The invention accordingly relates also to a cosmetic preparation orformulation comprising from 0.0001 to 90% by weight of a pigment,especially an effect pigment, according to the invention and from 10 to99.9999% of a cosmetically suitable carrier material, based on the totalweight of the cosmetic preparation or formulation.

Such cosmetic preparations or formulations are, for example, lipsticks,blushers, foundations, nail varnishes and hair shampoos.

The pigments may be used singly or in the form of mixtures. It is, inaddition, possible to use pigments according to the invention togetherwith other pigments and/or colorants, for example in combinations asdescribed hereinbefore or as known in cosmetic preparations. Thecosmetic preparations and formulations according to the inventionpreferably contain the pigment according to the invention in an amountfrom 0.005 to 50% by weight, based on the total weight of thepreparation.

Suitable carrier materials for the cosmetic preparations andformulations according to the invention include the customary materialsused in such compositions. The cosmetic preparations and formulationsaccording to the invention may be in the form of, for example, sticks,ointments, creams, emulsions, suspensions, dispersions, powders orsolutions. They are, for example, lipsticks, mascara preparations,blushers, eye-shadows, foundations, eyeliners, powder or nail varnishes.

If the preparations are in the form of sticks, for example lipsticks,eye-shadows, blushers or foundations, the preparations consist for aconsiderable part of fatty components, which may consist of one or morewaxes, for example ozokerite, lanolin, lanolin alcohol, hydrogenatedlanolin, acetylated lanolin, lanolin wax, beeswax, candelillia wax,microcrystalline wax, carnauba wax, cetyl alcohol, stearyl alcohol,cocoa butter, lanolin fatty acids, petrolatum, petroleum jelly, mono-,di- or tri-glycerides or fatty esters thereof that are solid at 25° C.,silicone waxes, such as methyloctadecane-oxypolysiloxane andpoly(dimethylsiloxy)-stearoxysiloxane, stearic acid monoethanolamine,colophane and derivatives thereof, such as glycol abietates and glycerolabietates, hydrogenated oils that are solid at 25° C., sugar glyceridesand oleates, myristates, lanolates, stearates and dihydroxystearates ofcalcium, magnesium, zirconium and aluminum.

The fatty component may also consist of a mixture of at least one waxand at least one oil, in which case the following oils, for example, aresuitable: paraffin oil, purcelline oil, perhydrosqualene, sweet almondoil, avocado oil, calophyllum oil, castor oil, sesame oil, jojoba oil,mineral oils having a boiling point of about from 310 to 410° C.,silicone oils, such as dimethylpolysiloxane, linoleyl alcohol, linolenylalcohol, oleyl alcohol, cereal grain oils, such as wheatgerm oil,isopropyl lanolate, isopropyl palmitate, isopropyl myristate, butylmyristate, cetyl myristate, hexadecyl stearate, butyl stearate, decyloleate, acetyl glycerides, octanoates and decanoates of alcohols andpolyalcohols, for example of glycol and glycerol, ricinoleates ofalcohols and polyalcohols, for example of cetyl alcohol, isostearylalcohol, isocetyl lanolate, isopropyl adipate, hexyl laurate and octyldodecanol.

The fatty components in such preparations in the form of sticks maygenerally constitute up to 99.91% by weight of the total weight of thepreparation. The cosmetic preparations and formulations according to theinvention may additionally comprise further constituents, such as, forexample, glycols, polyethylene glycols, polypropylene glycols,monoalkanolamides, non-coloured polymeric, inorganic or organic fillers,preservatives, UV filters or other adjuvants and additives customary incosmetics, for example a natural or synthetic or partially synthetic di-or tri-glyceride, a mineral oil, a silicone oil, a wax, a fatty alcohol,a Guerbet alcohol or ester thereof, a lipophilic functional cosmeticactive ingredient, including sun-protection filters, or a mixture ofsuch substances.

A lipophilic functional cosmetic active ingredient suitable for skincosmetics, an active ingredient composition or an active ingredientextract is an ingredient or a mixture of ingredients that is approvedfor dermal or topical application. The following may be mentioned by wayof example:

-   -   active ingredients having a cleansing action on the skin surface        and the hair; these include all substances that serve to cleanse        the skin, such as oils, soaps, synthetic detergents and solid        substances;    -   active ingredients having a deodorizing and        perspiration-inhibiting action: they include antiperspirants        based on aluminum salts or zinc salts, deodorants comprising        bactericidal or bacteriostatic deodorizing substances, for        example triclosan, hexachlorophene, alcohols and cationic        substances, such as, for example, quaternary ammonium salts, and        odour absorbers, for example Grillocin® (combination of zinc        ricinoleate and various additives) or triethyl citrate        (optionally in combination with an antioxidant, such as, for        example, butyl hydroxytoluene) or ion-exchange resins;    -   active ingredients that offer protection against sunlight (UV        filters): suitable active ingredients are filter substances        (sunscreens) that are able to absorb UV radiation from sunlight        and convert it into heat; depending on the desired action, the        following light-protection agents are preferred:        light-protection agents that selectively absorb sunburn-causing        high-energy UV radiation in the range of approximately from 280        to 315 nm (UV-B absorbers) and transmit the longer-wavelength        range of, for example, from 315 to 400 nm (UV-A range), as well        as light-protection agents that absorb only the        longer-wavelength radiation of the UV-A range of from 315 to 400        nm (UV-A absorbers);    -   suitable light-protection agents are, for example, organic UV        absorbers from the class of the p-aminobenzoic acid derivatives,        salicylic acid derivatives, benzophenone derivatives,        dibenzoylmethane derivatives, diphenyl acrylate derivatives,        benzofuran derivatives, polymeric UV absorbers comprising one or        more organosilicon radicals, cinnamic acid derivatives, camphor        derivatives, trianilino-s-triazine derivatives,        phenyl-benzimidazolesulfonic acid and salts thereof, menthyl        anthranilates, benzotriazole derivatives, and/or an inorganic        micropigment selected from aluminum oxide- or silicon        dioxide-coated TiO₂, zinc oxide or mica;    -   active ingredients against insects (repellents) are agents that        are intended to prevent insects from touching the skin and        becoming active there; they drive insects away and evaporate        slowly; the most frequently used repellent is diethyl toluamide        (DEET); other common repellents will be found, for example, in        “Pflegekosmetik” (W. Raab and U. Kindl, Gustav-Fischer-Verlag        Stuttgart/New York, 1991) on page 161;    -   active ingredients for protection against chemical and        mechanical influences: these include all substances that form a        barrier between the skin and external harmful substances, such        as, for example, paraffin oils, silicone oils, vegetable oils,        PCL products and lanolin for protection against aqueous        solutions, film-forming agents, such as sodium alginate,        triethanolamine alginate, polyacrylates, polyvinyl alcohol or        cellulose ethers for protection against the effect of organic        solvents, or substances based on mineral oils, vegetable oils or        silicone oils as “lubricants” for protection against severe        mechanical stresses on the skin;    -   moisturizing substances: the following substances, for example,        are used as moisture-controlling agents (moisturizers): sodium        lactate, urea, alcohols, sorbitol, glycerol, propylene glycol,        collagen, elastin and hyaluronic acid;    -   active ingredients having a keratoplastic effect: benzoyl        peroxide, retinoic acid, colloidal sulfur and resorcinol;    -   antimicrobial agents, such as, for example, triclosan or        quaternary ammonium compounds;    -   oily or oil-soluble vitamins or vitamin derivatives that can be        applied dermally: for example vitamin A (retinol in the form of        the free acid or derivatives thereof), panthenol, pantothenic        acid, folic acid, and combinations thereof, vitamin E        (tocopherol), vitamin F; essential fatty acids; or niacinamide        (nicotinic acid amide);    -   vitamin-based placenta extracts: active ingredient compositions        comprising especially vitamins A, C, E, B₁, B₂, B₆, B₁₂, folic        acid and biotin, amino acids and enzymes as well as compounds of        the trace elements magnesium, silicon, phosphorus, calcium,        manganese, iron or copper;    -   skin repair complexes: obtainable from inactivated and        disintegrated cultures of bacteria of the bifidus group;    -   plants and plant extracts: for example arnica, aloe, beard        lichen, ivy, stinging nettle, ginseng, henna, chamomile,        marigold, rosemary, sage, horsetail or thyme;    -   animal extracts: for example royal jelly, propolis, proteins or        thymus extracts;

cosmetic oils that can be applied dermally: neutral oils of the Miglyol812 type, apricot kernel oil, avocado oil, babassu oil, cottonseed oil,borage oil, thistle oil, groundnut oil, gamma-oryzanol, rosehip-seedoil, hemp oil, hazelnut oil, blackcurrant-seed oil, jojoba oil,cherry-stone oil, salmon oil, linseed oil, cornseed oil, macadamia nutoil, almond oil, evening primrose oil, mink oil, olive oil, pecan nutoil, peach kernel oil, pistachio nut oil, rape oil, rice-seed oil,castor oil, safflower oil, sesame oil, soybean oil, sunflower oil, teatree oil, grapeseed oil or wheatgerm oil.

The preparations in stick form are preferably anhydrous but may incertain cases comprise a certain amount of water which, however, ingeneral does not exceed 40% by weight, based on the total weight of thecosmetic preparation.

If the cosmetic preparations and formulations according to the inventionare in the form of semi-solid products, that is to say in the form ofointments or creams, they may likewise be anhydrous or aqueous. Suchpreparations and formulations are, for example, mascaras, eyeliners,foundations, blushers, eye-shadows, or compositions for treating ringsunder the eyes.

If, on the other hand, such ointments or creams are aqueous, they areespecially emulsions of the water-in-oil type or of the oil-in-watertype that comprise, apart from the pigment, from 1 to 98.8% by weight ofthe fatty phase, from 1 to 98.8% by weight of the aqueous phase and from0.2 to 30% by weight of an emulsifier.

Such ointments and creams may also comprise further conventionaladditives, such as, for example, perfumes, antioxidants, preservatives,gel-forming agents, UV filters, colorants, pigments, pearlescent agents,non-coloured polymers as well as inorganic or organic fillers.

If the preparations are in the form of a powder, they consistsubstantially of a mineral or inorganic or organic filler such as, forexample, talcum, kaolin, starch, polyethylene powder or polyamidepowder, as well as adjuvants such as binders colorants etc.

Such preparations may likewise comprise various adjuvants conventionallyemployed in cosmetics, such as fragrances, antioxidants, preservativesetc.

If the cosmetic preparations and formulations according to the inventionare nail varnishes, they consist essentially of nitrocellulose and anatural or synthetic polymer in the form of a solution in a solventsystem, it being possible for the solution to comprise other adjuvants,for example pearlescent agents.

In that embodiment, the coloured polymer is present in an amount ofapproximately from 0.1 to 5% by weight.

The cosmetic preparations and formulations according to the inventionmay also be used for colouring the hair, in which case they are used inthe form of shampoos, creams or gels that are composed of the basesubstances conventionally employed in the cosmetics industry and apigment according to the invention.

The cosmetic preparations and formulations according to the inventionare prepared in conventional manner, for example by mixing or stirringthe components together, optionally with heating so that the mixturesmelt.

The Examples that follow illustrate the invention without limiting thescope thereof. Unless otherwise indicated, percentages and parts arepercentages and parts by weight, respectively.

EXAMPLES Example 1

Two separate evaporators arranged in a vacuum chamber (<10⁻¹ Pa) are fedwith SiO and NaCl powder, respectively. A rotating carrier to which analuminum foil is attached mechanically is arranged above theevaporators. A NaCl layer (90 nm) is first sublimated onto the aluminumfoil. Then the SiO evaporator is heated and the SiO begins to sublimatewhile salt is still sublimated. In this manner salt and SiO aresublimated simultaneously onto the NaCl layer. The simultaneousvaporization of salt and SiO is continued until a thickness of 300 nm isachieved. Sublimation is terminated, the aluminum foil of the carrier isremoved and immersed into distilled water. The NaCl layer as well as thesalt contained in the SiO matrix resolve in water, whereby silicon oxideflakes are obtained. Porous SiO₂ flakes can be obtained by heating thesilicon oxide flakes in air at a temperature greater than 500° C. forseveral hours, if the SiO_(y) has not completely been converted to SiO₂by normal work-up.

FIG. 3 shows an atomic force microscope (AFM) picture of the porous SiO₂flakes of example 1 (BET=712 m²/g). The pore sizes are up to 30 nm.

Example 2

A vacuum chamber is loaded with 2 crucibles which each have an ownenergy supply. The first crucible is filled with SiO and the secondcrucible with NaCl. The vaporization rate of the materials can bemeasured by means of a quartz resonator (oscillator quartz). Theevaporators are separated by a flap valve from the rustless steelsubstrate.

The crucible containing NaCl is heated up until the quartz resonatorindicates a vaporization rate of 0.3±0.04 nm/s. The flap valve is openeduntil a NaCl-Schicht has been sublimated onto the rustless steelsubstrate having a thickness of 100 nm. The cap is then closed.

While the NaCl crucible is hold at the same temperature, the cruciblecontaining SiO is heated until the oscillator quartz indicates avaporization rate of 2.8±1.2 nm. The flap valve is then opened. Theco-sublimation of NaCl and SiO is continued until a total thickness of420 nm is achieved. The SiO evaporator is then disconnected, the NaClevaporator is operated about 100 s and then the flap valve is closed.

The substrate is taken from the vacuum chamber. The salt is dissolved inwater, the obtained silicon oxide flakes are washed with water anddried. The analysis by means of high-resolution electron microscopyshows, that the silicon oxide flakes show pores with a diameter of about10.5 nm.

Porous SiO₂ flakes can be obtained by heating the silicon oxide flakesin air at a temperature greater than 500° C. for several hours, if theSiO_(y) has not completely been converted to SiO₂ by normal work-up.

Example 3

0.27 g (4.49 mmol) porous SiO₂ obtained in example 1 (BET=712 m²/g) aremixed in a 100 ml round bottom flask under N₂ with 10.0 g (52.7 mmol)TiCl₄ and stirred over night (17 h) at room temperature with a magneticstirrer, whereby the TiCl₄ reacted with the adsorbed water to formnano-TiO₂. The excess of the TiCl₄ is removed in vacuo and the solidmass dried in a rotary evaporator at 80° C., p=0.01 mbar. Ca. 0.3 g of agrey powder showing interference colors is obtained.

Elemental Analysis: 0.47% C, 2.23% H, <0.3% Cl, 12.40% Ti, correspondingto a TiO₂ content of ca. 20 wt. %.

Example 4

The coating formulations used in this example are described in the tablebelow.

Sample 1 Sample 2 Ingredient Description (inventive) (comparative)porous silica flakes silica flakes 100 — of example 1 Sipernat (Degussaprecipitated silica — 80 AG) MOX (Degussa AG) fused silica — 20 Celvol(Celanese) Polyvinylalcohol 30 30 DP6 (Ciba SC) Polyvinylpyrrolidon 1.31.3 (PVP)

All coatings are applied on an uncoated freesheet (Xerographic paper,distributed by Corporate Express, basis weight 75 g/m², 21.59 cm×27.94cm, TAPPI brightness 84) using a hand drawdown coater (K303 Multicoater,RK Print-Coat Instruments) to target a low (3 g/m²) and a high (4.5g/m²) coatweight.

Due to its high viscosity, the sample 1 has to be made down at lowersolids (12%) versus the sample 2 (19%), in order to be able to coat iton the hand drawdown coater.

The coated paper containing sample 1 displays a metallic pearlescenttexture.

In addition, the coatings containing sample 1 showed a higherwashfastness (Washfastness: drip test as per HP's specifications (2 mlwater, 45′ angle) to determine:

ΔE=√{square root over (ΔL*²+Δa*²+Δb*²)}) than the coatings containingsample 2.

Example 5 a) Preparation of Porous Silica Containing Metallic PalladiumNanoparticles

500 mg porous SiO₂ (BET 750 m²/g) obtained in analogy to the processdescribed in example 1 and 53 mg of [(C₆H₄CH₂NMe₂-2)Pd(OAc)(PPh₃)] (asdescribed in WO03/13723), a well-defined palladium complex which slowlydecomposes upon heating, are mixed in 5 ml xylene. This mixture isstirred rigorously and heated to reflux under a nitrogen atmosphere, andkept at this temperature for 2 hours. During this period of time thecolor of the reaction mixture turned black. After cooling to roomtemperature the porous silica was isolated by filtration and washed oncewith xylene and three times with diethyl ether. The grey silica wasdried in vacuum. 506 mg of grey colored porous silica was obtained. Anelemental analysis showed that the material contains 1.75 percent byweight palladium (see FIG. 2, which is an ultrathin section of a porousSiO₂ flake loaded with palladium).

b) Suzuki Coupling Using the Immobilized Palladium Catalyst on PorousSilica from Example 5a

190 mg 3-bromoanisole, 183 mg phenyl boronic acid and 275 mg potassiumcarbonate are mixed in 2 ml xylene. To this is added 27 mg of thecatalyst from example 5a (corresponds to 0.5 mol % palladium). Thereaction mixture is stirred and heated, under an atmosphere of nitrogen,to a temperature of 130° C. for a period of 2 hours. A GC analysisshowed that all starting material is consumed and 3-methoxy biphenyl isformed selectively (100% conversion).

After cooling the reaction mixture to room temperature, the catalyst isisolated by filtration and washed subsequently with xylene, ethanol,water, ethanol and diethyl ether, and dried in vacuum. A second run withthis catalyst under the same conditions is performed. A GC analysis ofthe reaction mixture showed again a high conversion to 3-methoxybiphenyl (>80% conversion).

Example 6

0.600 g porous SiO₂ (BET: 660 m²/g) obtained in analogy to the processdescribed in example 1 having a maximum particle size of 40 μm aresuspended in 35 ml water and heated in a four-neck flask in an oil bathto 65° C. with stirring. The pH of the suspension is controlled with 1NHCl to 1.4. Then, 24 ml of an aqueous TiOCl₂ solution (0.5% Ti)stabilised by conc. HCl are added at 65° C. within 8 hours under anatmosphere of nitrogen. The pH is kept constant at 1.4 by slow additionof an aqueous 2N NaOH solution. After the addition of TiOCl₂ has beenfinished, the suspension is stirred for additional 30 minutes. Then thelight-blue suspension is cooled to 25° C., filtered with a 20 μm sieve,washed with water and methanol and dried at 50° C. in vacuo, whereby alight-blue product (BET: 650 m²/g) is obtained. The TiO₂ content of theproduct is ca. 8.2% by weight.

Example 7

500 mg of C.I. Pigment Red 179 are dissolved in 60 g of sulphuric acid(96%) at room temperature and stirred for an hour. 500 mg of porous SiO₂flakes (BET: 700 m²/g) obtained in analogy to the process described inexample 1 are added in portions to the dark violet solution portionunder stirring. Then the suspension is stirred for 2 hours. Thereafter60 g of glacial water are slowly added to the suspension under stirring,wherein the pigment is precipitated into the pores of the porous SiO₂and an intensive red colored pigment is obtained. 1000 ml of de-ionizedwater are added to the red suspension and the obtained suspension isstirred for 30 minutes, filtered, washed with water and dried in vacuo.A red composite pigment is obtained.

Example 8

200 mg of

are dissolved in a mixture consisting of 10 g 1-methyl-2-pyrrolidone(NMP) and 25 g of ethanol (99%). To this solution 2 g of porous SiO₂flakes (BET: 700 m²/g) obtained in analogy to the process described inexample 1 are added and heated to 60° C. 25 g of ethanol (99%) are addedand the suspension is stirred for further 2 h at 60° C. 1000 ml of waterare added to the homogenous suspension at 60° C. under stirring within afew seconds, where the latent pigment is precipitated. The yellow orangesuspension is cooled to room temperature under stirring, filtered andwashed with 1000 g de-ionized water and dried for 16 h at roomtemperature and subsequently 12 h in a vacuum oven at 100° C. (100 hPa).The slightly pink powder is heated to 180° C. for 20 minutes, where acomplete elimination of the BOC groups is achieved. A red compositepigment results.

Example 9

500 mg of porous SiO₂ flakes (BET: 700 m²/g) obtained in analogy to theprocess described in example 1 are suspended in a diluted solution of 4g FeCl₃×6H₂O in 150 de-ionized water and stirred for 6 h at 50° C. ml.Thereafter a 4% solution of sodium hydroxide is slowly added dropwiseunder stirring, until a dark brown precipitate results (pH 3.5). Thesuspension is stirred for 12 h, filtered and the filter cake is rinsedwith 4% hydrochloric acid and 1000 g de-ionized water. The golden yellowprecipitate is first dried 16 h at room temperature and then 12 h in avacuum oven at 100° C. (100 hPa). A golden yellow composite-pigment isobtained, which can optionally be calcinated at 700-850° C.

1. A porous platelike SiO_(z) flake, wherein 0.70≦z≦2.0, which flake hasa BET specific surface area of greater than 500 m²/g, is characterizedby a plane-parallelism and a defined thickness in the range of ±10% ofthe average thickness, and contain pores which are randomlyinter-connected in a three-dimensional way, obtained by a processcomprising the steps a) vapor-deposition of a separating agent onto acarrier to produce a separating agent layer, b) the simultaneousvapor-deposition of a material selected from SiO_(z), Si and a mixturethereof, and a separating agent onto the separating agent layer (a), c)the separation of the material from the separating agent.
 2. A porousplatelike SiO_(z) flake according to claim 1, wherein in step b of theprocess consists of the simultaneous vapor-deposition of SiO_(z), and aseparating agent onto the separating agent layer (a).
 3. A porousplatelike SiO_(z) flake according to claim 1, wherein in step b of theprocess, a SiO_(y)/separating agent layer, wherein 0.70≦y≦1.8, isvapor-deposited from two different vaporizers, wherein the firstvaporiser contains a charge comprising a mixture of Si and SiO₂, SiO_(y)or a mixture thereof, and the second vaporiser containing a chargecomprising the separating agent.
 4. A porous platelike SiO_(z) flakeaccording to claim 3, wherein the process comprises a further stepwherein the SiO_(y) is converted to SiO_(z) with 1.40≦z≦2.0 by heatingin an oxygen-containing atmosphere, or to SiO_(y+a), containing(1−(y/y+a)) silicon, wherein 0.70≦y≦1.8, 0.05≦a≦1.30, and the sum of yand a is smaller or equal to 2, by heating SiO_(y) in an oxygen-freeatmosphere.
 5. A porous platelike SiO_(y+a) flake according to claim 4.